An inventory of the vascular plants of Heil Valley Ranch and Hall Ranch in the north foothills of Boulder County was completed during 2017 and 2018, prior to a catastrophic forest fire that severely impacted this area in the fall of 2020. Heil Valley Ranch and Hall Ranch are keystone units of the Boulder County Parks and Open Space system. These large parcels (∼10,000 acres/4047 ha) represent a significant portion of publicly accessible open space in the county and represent an exemplary legacy of land preservation in the region. The biologically diverse foothill landscapes represent the ecotone between the High Plains and the Southern Rocky Mountains. Vital transition zones in the area harbor globally vulnerable and critically imperiled plant associations, the most detailed categorization described by the US National Vegetation Classification (2021). A total of 607 botanical specimens were collected over the course of 39 separate visits. There are 381 species from 82 families of flowering plants represented at the study area, with the greatest diversity occurring in Poaceae and the Asteraceae. Of these, 319 are native, 62 are non-native, and 7 species are of conservation concern. The present study is the first floristic study of these parcels and provides baseline data for future work in the area, as well as information for comparison to floristic works in the broader Front Range foothills region. Together, these studies inform conservation policy at a time when biodiversity is threatened both globally and locally. As the Front Range megaregion rapidly expands in human population, biological inventories will provide critical data to promote the expansion of conservation areas in parallel with urban growth.
Natural history collections contribute critical data to many disciplines that address questions and challenges pertaining to biodiversity, but also to the identification and production of foods, medicines, and knowledge about diseases (Funk 2018). The material generated by floristic inventories specifically contributes to policy planning for the placement of conservation areas and for the protection of species of conservation concern (Nualart et al. 2017). Spatial and temporal data encapsulated in a museum specimen are exceptional resources that not only facilitate research in taxonomy and systematics, but also help to advance informal learning and scientific literacy (Monfils et al. 2017). The Front Range Urban Corridor is a populous region spanning the eastern edge of the Southern Rocky Mountains that is part of a fast-growing megaregion anchored by Denver (Lang et al. 2007). This study provides baseline data given the anthropogenic threats such as habitat fragmentation, development, and climate change. Floristic inventories have the potential to play a profound role in the necessary synthesis between urban planning and conservation in the foothills of the Southern Rockies. As cities in this region merge, conservation areas will also require expanded networks to provide robust and contiguous habitat necessary to support functional and thriving populations of flora, fauna, and microbiota.
The emergence of the Rocky Mountain Chain approximately 70 million yr ago generated a landscape characterized by substantive relief. This mountain building event and the recession of the Western Interior Seaway apportioned a complex geology and diversity of life zones (Mutel and Emerick 1992; Bridge 2004). In Boulder County, the Southern Rockies extend to their eastern terminus, bringing the Continental Divide near the burgeoning Front Range Urban Corridor. Within the 742 square miles comprising Boulder County, most of Colorado's life zones are present, from alpine tundra to grassland. There are 3324 flowering plant taxa documented within Colorado (Ackerfield 2015), and remarkably, over half of these (1743 taxa) occur in Boulder County alone (Weber 1995).
Heil Valley Ranch and Hall Ranch are administered by Boulder County Parks and Open Space (BCPOS). At the time of their acquisition in the early 1990s (along with Trevarton Ranch), these two properties represented one of the largest land rescues in the county (BCPOS 1996). Heil Valley and Hall Ranches (Fig. 1) offer unique opportunities not only for recreation, but also for increasing awareness about the ecological, genetic, and aesthetic benefits of this unique intersection of grasslands and the mountain foothills (Bock and Bock 1998). Along with the City of Boulder Mountain Parks, the Arapaho and Roosevelt National Forests, Ron Stewart Preserve at Rabbit Mountain and other BCPOS parcels, Heil Valley Ranch and Hall Ranch provide a critical refuge for the flora and fauna of the northern foothills of Boulder County. The substantial size of these two parcels (6231 and 3899 acres respectively) makes them a significant addition to a long legacy of natural area conservation in the county.
The objective of the present work is to provide the first repository of plant biodiversity data of an ecologically complex foothills ecotone, where there has never been a thorough floristic inventory. The lack of collecting in these foothill ecotones is notable in a county with an extensive (approximately 170 yr) history of botanical collecting. Important contributions to collecting in Boulder County have been made by Frances Ramaley, William A. Weber, Tim Hogan, and Dina Clark (SEINet) among many others. The parcels were privately owned up until their acquisition by BCPOS in the early 1990s. It is at this time that thorough inventories of the plant communities and biologically significant portions at the study area were conducted by the BCPOS (1996, 2016) and CNHP (Brune et al. 1996; Neid et al. 2008), but none have produced a comprehensive checklist of the flora. Neid et al. (2008) coalesced data (including private lands) that identified rare species, plant communities of concern and proposed habitat for conservation in Boulder County. Prior to 2017, 12 botanists had sampled plants from the study area, yielding 65 specimens.
The present study aims to comprehensively survey the plants of Heil Valley Ranch and Hall Ranch. This work has the potential to inform management decisions of BCPOS, especially after catastrophic wildfires that traversed the region in late 2020, devastating approximately 5000 acres of Heil Valley Ranch in particular (BCPOS 2021). The inventory can also be used towards comparative study regarding inventories of adjacent natural areas in the county and beyond. These data have applications for comparison with the work of Hogan (1993, 2019) and Clark (2014). In addition, recent inventories of the Red Hill Study Area (an area of high biodiversity significance on Heil Valley Ranch and Trevarton Open Space) (Vickery 2019), as well as Ron Stewart Preserve at Rabbit Mountain (Vickery 2021) demonstrate increased attention to the biodiversity of the foothills, where species from the great plains reach the edge of their range. Going further, significant shrublands and grasslands at the study area offer grounds for wider comparison to adjacent foothill sites north and south, including Red Mountain and Soapstone Prairie Natural Area in Larimer County (Brune et al. 1996; McAleer 2014) and inventories of Golden and vicinity (Schweich 2020a, 2020b; CNHP 2021) in Jefferson County. Inventories of grasslands in eastern Colorado such as Pawnee National Grassland (Hazlett 1998), Mesa de Maya (Clark 1996), and Comanche National Grassland (Kuhn 2009) also aid in our understanding of these underrepresented landscapes.
The purpose of the study is to provide a checklist of the flora at each parcel that can be utilized by staff at BCPOS for conservation planning. This work contributes to the list of floras in the region that together provide a basis for reference ecosystems that can be used to inform restoration policy and the assessment of the level of degradation of an area (Nualart et al. 2017). In addition, this checklist can be used to support interpretation that increases scientific literacy and engages the public at these popular recreation destinations.
Description of the Study Area
Heil Valley Ranch and Hall Ranch together encompass approximately 10,000 acres (4047 ha) (Fig. 1). The elevation gradient spans nearly 609 meters at Hall Ranch (1643 to 2195 meters) and nearly 823 meters (∼1646 to 2463 meters) at Heil Valley Ranch. On a north-south axis, the parcels are separated by South St. Vrain Drive (Colorado Route 7) and the South St. Vrain Creek. The eastern boundary consists of points that converge with U.S. Route 36: the town of Lyons, Colorado Route 7, and several BCPOS conservation easements and Left-hand Canyon. The Dakota Hogback, a series of north to south trending sandstone hills, occurs to the west of Route 36, marking the transition between the Great Plains and the Rocky Mountains (Waagé 1955). The Western boundary is predominately under jurisdiction of the United States Forest Service (i.e., Arapahoe and Roosevelt National Forests). The location of the study area positions it as critical buffer between the Front Range Urban Corridor and these adjacent national forests. Notably, the study area itself harbors significant populations of flora and fauna that rely on the wide assortment of habitats present in this ecotone. The occurrence of shrublands, which are unique within Boulder County, offers resources for numerous mammals and birds. The study area also provides winter refuge for migrating mammals, and habitat for butterflies that prefer high quality tallgrass prairies (Neid et al. 2008). Hall Ranch is also home to the highest elevation prairie dog colonies in Boulder County (BCPOS 1996).
Heil Valley Ranch comprises approximately 6231 acres (2,522 ha). Large areas are set aside for habitat conservation (∼5000 acres). Two-hundred forty-three acres are set aside for raptors as seasonal closures between December 15 and July 15. Recreation is not permitted in those areas. Most of the critical wildlife habitat is located on the west side of the parcel bordering Arapaho and Roosevelt National Forests. Significant features include secluded canyons, remnants of ranching settlements and quarries, a box canyon, and seasonal ponds.
Hall Ranch encompasses approximately 3899 acres (1578 ha) and is located west of the town of Lyons between the North and South St. Vrain Creeks. Approximately 1718 acres are designated, for habitat conservation where recreation is not permitted. The parcel consists of grasslands and shrublands to the east and woodlands and lower montane forest to the west. Two charismatic land formations occur at Hall Ranch: Indian Lookout Mountain and Hat Rock, which exist in close proximity to the primary parking area of Hall Ranch and the town of Lyons. To the northwest, Hall Ranch connects with the Button Rock Preserve (City of Longmont) via the Button Rock Trail.
The mountain building event of the Laramide orogeny (approximately 75 to 40 million yr ago) exposed a complex geology, consisting of igneous, sedimentary, and metamorphic rock units in the study area. Sandstone is the most common rock unit. The western portions of Hall Ranch include igneous rocks of Silver Plume Granite and sedimentary layers of the Fountain Formation, Ingleside Formation, and Lyons Sandstone. West of the town of Lyons, the peaks of Indian Lookout Mountain and Hat Rock are composed of the Ingleside formation (reddish-pink, fine-grained quartz sandstone). Surrounding the peaks is the Fountain Formation (arkosic conglomerate, sandstone, siltstone, shale and limestone). Sedimentary rock units prevail at Heil Valley Ranch. These include the Fountain Formation, Lyons Sandstone, and Lykins Formation. The northern area of Heil Valley Ranch is composed of Lyons Sandstone and Bergen Shale. The maroon cast of Red Hill, in the eastern portion of the parcel is the result of siltstone and sandstone of the Lykins formation. Plumely Canyon and Geer Canyon, in the western portion of the parcel, are composed of the Fountain Formation (sandstone, siltstone and shale) (Braddock et al. 1988; BCPOS 1996).
Land Use History
It is likely that the region has been occupied by humans since the late Pleistocene. Paleoindians were present between 11,300–7500 radiocarbon yr before present (Pitblado et al. 2007). The tribes of the eastern plains included the Apache, Comanche, Kiowa, Pawnee, and Shoshonee (Hughes 1987). Ute tribes inhabited the Central Rocky Mountains (Buchholtz 1983; Hughes 1987). Arapaho and Cheyenne tribes inhabited the area now known as Hall Ranch. Contact with Europeans began 275 yr before present. Evidence of tribal activity exists to this day, as four native American sites exist at Heil Valley Ranch (BCPOS 2022). Cultural sites include domestic structures, quarries, and rock art (BCPOS 1996).
The 1700s and 1800s were marked by exploration and fur trading by the Spanish and other European colonists. Beaver trappers worked in the surrounding rivers. The subsequent gold rush of the mid 19th century led to the pursuit of mining. Agriculture returned to prominence in the 19th century (Noel 2015). With expansion, builders sought new materials to replace wood and brick. Quarries in the study area produced the characteristic Lyons sandstone that has been used to build many local structures, including those of the University of Colorado Boulder campus. Throughout the 20th century, land use at both properties included homesteading, cattle ranching, and grazing of livestock. Harvest on these sites included crops, hay, and timber. Hunting occurred, primarily for deer and elk, mountain lion, black bear, and wild turkey. Moss rock collecting also took place (BCPOS 2022). The two properties were acquired in 1993 and 1994 by Boulder County and an additional 210 acres were added to Heil Valley Ranch in 2012 (BCPOS 1996, 2016).
The study area is located at the convergence of the High Plains and the Southern Rocky Mountains and features climatic elements of the high plains, mid-continental, and mountain ecoregions. The climate is semi-arid, with an increase in precipitation in the higher elevations towards the west (BCPOS 1996; Doesken 2003). Average precipitation for the nearby city of Longmont is 358.9 mm per yr. The average annual high temperature is 64.7°F and the low is 33.2°F. The warmest month of the year is July with average high temperatures of 89°F. January is the coolest month with average high temperatures of 42°F and low temperatures of 12°F (U.S. Climate Data 2019). The outer hogbacks of the study area receive more wind and sun exposure, allowing them to harbor higher concentrations of xerophytic plant associations, such as the characteristic Cercocarpus montanus Raf. (Mountain Mahogany) shrublands (Neid et al. 2008).
To produce a first checklist of the flowering plants of Heil Valley Ranch and Hall Ranch and facilitate downstream conservation planning, 39 d were spent collecting plants in the field during the growing seasons of 2017 (June 14–August 15) and 2018 (April 30–September 30).
To facilitate the planning of fieldwork, the first author (SW) surveyed aerial maps and documentation of the study area prior to site visits. Sites were selected on the basis of diversity in topography, moisture, and aspect. While efforts were made to explore the majority of each parcel, subjective sampling was conducted in order to ensure the collection of as much diversity as possible (Peet 1981). Most species (229/381) were collected only once, in adherence to the guidelines set by BCPOS. Numerous species (152) were collected twice or more, when they belonged to larger plant families such as the Asteraceae, Cyperaceae, Fabaceae, and Poaceae, groups that were more challenging to key out in the field. Non-native species were also collected more than once in order to assess their impact on the landscape. Areas designated as critical wildlife habitat were visited only with permission from BCPOS and collecting in those areas was limited to late summer after the golden eagle nesting season. In addition, the following inventories were consulted: Clark (1996, 2014), Hogan (1993, 2019), Kuhn (2009), Sharples (2017), Tripp (2015), and Weber (1995).
At each collection site, a GPS waypoint was taken to record latitude, longitude, and elevation. Field notes were taken to record salient features pertaining to habitat, community vegetation type, and aspect. An approximate assessment of abundance was made for common species, while less common species were counted in the field prior to collecting. The following rankings used in the checklist are estimates: abundant (>1000), common (>500), scattered (∼100), uncommon (<50), and rare (<25). In cases where there were less than 25 of a species, a photograph and coordinates were taken, and herbarium records were consulted prior to collecting.
Five collecting sites are outside of the boundary for either ranch. The species collected at these sites are included in the inventory because they are unique to study area. At two lower montane sites at Hall Ranch, several unique species were found including: Arabis pycnocarpa M.Hopkins, Goodyera oblongifolia Raf., Heuchera bracteata (Torr.) Ser., and Turritis glabra L. Two species were collected at Trevarton Open Space: Oenothera howardii (A.Nelson) M.E.Jones ex Prain and Triodanis leptocarpa (Nutt.) Nieuwl. Near the saddle of Geer Canyon, at Heil Valley Ranch the first author collected Castilleja miniata Douglas ex Hook., Orthocarpus luteus Nutt., and Oxytropis lambertii Pursh.
A preliminary taxonomic identification was assigned in the field when possible. Plants were pressed in folded newspaper in a field press and later transferred into a wooden plant press between blotters and cardboard upon return from the study area. Within 24 hr, the plant presses were placed into the oven at University of Colorado Herbarium (COLO) and dried at 110°F for 2–3 d. The dried specimens were sorted by family and genus prior to final identification. After collection, specimens were identified, curated, and then deposited at COLO (Thiers 2022).
To identify collections, several references were used including the Colorado Flora Eastern Slope Fourth Edition (Weber and Wittmann 2012), The Flora of Colorado (Ackerfield 2015), and the Flora of North America (Flora of North America Editorial Committee 1993+). Plant taxonomy and nomenclature follow the Angiosperm Phylogeny Group III (2009). Each specimen identification was verified by utilizing the collection at COLO as a reference. Protologues and type specimens were also consulted in particularly difficult instances. Searches were conducted using SEINet (2022) to locate other specimens previously collected from the study area. Twelve botanists collected 65 specimens from the study area prior to this project. A map of the study area was generated with R (R, R Core Team, R Foundation for Statistical Computing, Vienna, Austria), using county open space, trail, and wildfire data from BCPOS (2022) and U.S. EPA Level III Ecoregions (U.S. EPA 2013).
Results And Discussion
A total of 381 species in 285 genera (and 82 families) were identified for the study area. Of the 82 families, the most taxonomically diverse were Poaceae (65), Asteraceae (61), Fabaceae (20), Rosaceae (17), and Cyperaceae (16). The most taxonomically diverse genera were Carex L. (8), Poa L. (7), and Astragalus L. (6). Three genera in the Poaceae were represented in the ten most diverse genera in the study area: Poa (7), Muhlenbergia Schreb. (5), and Bromus L. (5) (Table 1). Within the ten most species rich genera in the study area (Table 1), five are grass genera. There were 62 introduced species in the study area, comprising 16% of the flora. Sixteen species ranked as noxious weeds occur at the study area (Table 2). There are 7 species on the BCPOS Species of Special Concern List and the Colorado Natural Heritage Program (CNHP) tracking list (Table 3). A visual representation of the collections organized by genera and species is shown in Fig. 2.
The 10 Most Species-Rich Genera in the Study Area.
Introduced Species. Colorado noxious weed species are ranked in a hierarchy from A to C. B-list species are targeted by management plans designed to stop their spread. C-list species are targeted with management plans focused on education, research, and biological control. (Colorado Department of Agriculture 2019).
The Following Species Occur on the Boulder County Parks and Open Space Species of Special Concern List (BCPOS 2013) and the Colorado Natural Heritage Program (CNHP) Tracking List (2019). The heritage network ranking system is utilized to target at species and habitats of conservation concern. Global (G) and State (S) levels are indicated here. 1 = Critically imperiled, 2 = Imperiled, 3 = Vulnerable to Extirpation, 4 = apparently secure, 5 = Demonstrably Widespread, Abundant and Secure.* Two-Range Rank: Roughly equal chance of G2 or G3, but other ranks much less likely. (Master et al. 2012)
Below, we present a description of the plant communities present at the study area, these roughly following NatureServe's Terrestrial Ecological System descriptions (NatureServe 2013) based on observations made in the field. Here and elsewhere, vegetation classifications are useful in that they reflect synthesis between organisms and fundamental environmental factors, as well as ecological processes. Delimited units, for example, provide scientists the ability to communicate, conserve, and restore ecosystems. However, we caution that categorization of plant communities can undermine their complexity (Marr 1967; Peet 1981). For instance, species compositions within plant community types can fluctuate in response to environmental change, making simple classification schemes not entirely comprehensive. Finally, floods, fire suppression, and invasion by non-native species have also impacted plant community types within the study area (Peet 1981).
Grasslands. Grassland ecosystems in North America have been drastically impacted by destruction of habitat, grazing, and lack of awareness (Bock and Bock 1998). Grasslands present at the study area specifically include lower elevation ecotonal grasslands, meadows, and openings of the lower montane woodlands and forests, as well as introduced grasses that infiltrate these areas. At the study area, grasslands that intergrade with woodlands have, notably, been altered due to the encroachment of Pinus ponderosa P.Lawson & C.Lawson woodlands as a result of fire suppression and grazing (Brune et al. 1996).
Western Great Plains Foothill Grassland. Components of tallgrass prairie and mixed-grass prairie communities occur on the lower slopes of the Dakota hogback. They also appear in open woodland and savanna communities. Tallgrass prairie associations dominated by Andropogon gerardii Vitman (Fig. 3F) and Schizachyrium scoparium (Michx.) Nash include assemblages of both prairie and montane species (Brune et al. 1996). The Hesperostipa comata Colorado Front Range Grassland (G1G2/S2) is dominant in these lower grasslands and shrubland communities where it occurs in large expanses of open grassland and also in association with Cercocarpus montanus. The Hesperostipa neomexicana Grassland (G3/S2) (Fig. 3C) is a significant natural community occurring on shale slopes and rocky substrates. It is a common association in the southwestern US that reaches its northern limits in Colorado and Wyoming (Brune et al. 1996).
Rocky Mountain Foothill Shrubland. The Cercocarpus montanus system occurs on dry rocky slopes, often in dense concentrations (Neid et al. 2008). Vestal (1919) acknowledged the prominence of C. montanus on the exposed outer hogbacks of the Northern foothills in Boulder County. Hogan (2019) listed C. montanus as infrequent in the City of Boulder Mountain Parks. C. montanus occurs with other shrubs and grasses, and occasionally trees.
Rocky Mountain Foothill Riparian Shrubland. The Betula occidentalis Hook. alliance occurs along Geer Canyon Creek and is codominant with Acer glabrum Torr. This narrow channel is surrounded by mixed conifer forest and, although uncommon in the study area, is notable for its high plant diversity. Geer Canyon Creek is the primary natural hydrologic system that flows through Heil Valley Ranch. These shrublands are sequestered along the western boundary of the parcel.
Southern Rocky Mountain Conifer Forest and Woodland. This dominant ecological system presents in great variation over the study area. Pinus ponderosa encroaches on grasslands and shrublands at lower elevations, mingling with Cercocarpus montanus and Hesperostipa comata. It then shifts to dry woodlands with a sparse understory of currant, grasses, forbs, and succulents. An example of these xeric woodlands occurs west of the Nelson Loop at Hall Ranch. Higher in elevation, Ponderosa Pine forest increases in density and intersperses with Pseudotsuga menziesii (Mirb.) Franco in north facing ravines. These cool, sheltered slopes offer a diverse understory in this transition to the montane life zone. The dense stands are mixed in age with many saplings. Montane plants occur at the lower limit of their range. Populus tremuloides Michx. appears in clonal patches. Dry montane woodland occurs on and around rocky outcroppings, and west facing cliffs and ledges. Pseudotsuga menziesii and Pinus ponderosa emerge from rocky fissures. Asplenium septentrionale (L.) Hoffm. and A. trichomanes L. (Fig. 3B) are protected in horizontal crevices.
The present study represents the first floristic inventory of Heil Valley Ranch and Hall Ranch—two keystone units of conservation within Boulder County—as administered by Boulder County Parks and Open Space. Thorough inventories of the plant communities and biologically significant portions at the study area have been conducted by the BCPOS (1996, 2016) and CNHP (Brune et al. 1996; Neid et al. 2008), but none have produced a comprehensive checklist of the flora. The number of species reflects the diversity of habitats as well as land use history. Notably, the presence of semi-arid shrublands and extensive grasslands represents a departure from the forested foothills of Boulder Mountain Park. The present contribution provides data for comparison with relevant floristic work in the region, in particular to the concentrations of shrublands and high plains species in the county and along the Front Range. Within the study area there are 46 species with a high plains distribution. William Weber's 1995 checklist of Boulder County vascular plants provides a valuable overview of the rich flora found in the county (1538 taxa), a result of the steep topographical gradient in which the continental divide reaches its eastern expression. Floristic work by collection managers at COLO (Tim Hogan and Dina Clark) provide additional focus within the county.
Hogan's most recent work (2019) documents 698 species of vascular plants in Boulder Open Space and Mountain Parks, a neighboring area comparable in size (7000 acres) and provides a revised checklist that encompasses over 30 yr of collection in the area. Mountain Parks has differences in land use history, dominant plant communities, and lesser elevational gradient. In addition, it has benefitted from preservation measures enacted by the City of Boulder at the end of the 19th century, while the study area was acquired by BCPOS only in 1993 and 1994 (with ongoing expansions). Mountain Parks includes larger montane area and higher peaks. The terrain and geology at each location support different plant communities and concentrations of flora. Notable at Mountain Parks is the presence of 75 plant species with eastern North American affinities including Agrimonia striata Michx., Aralia nudicaulis L., Betula papyrifera Marshall, and Lilium philadelphicum L. In contrast, fewer of these eastern relics are present at the study area. Mountain Parks, for example, lacks large assemblage of foothills shrubland communities dominated by Cercocarpus montanus. These are supported by the rocky substrates and aspect provided by the Dakota Hogback. Twenty-one percent of the flora of the Boulder Mountain Park is composed of introduced species (Hogan 2019). Visual assessment coupled with the different land use histories of each site indicates that the impact of introduced species is more widespread and deleterious at the study area where semi-natural assemblages of introduced species dominate many of the grassland and woodland habitats.
Clark made 421 (of 898 retrieved from SEINet) collections at White Rocks Open Space (City of Boulder Open Space and Mountain Parks). This rare high plains habitat (∼100 acres) features Laramie and Fox Hills sandstone at the eastern edge of the county (Weber 1995; Tripp 2015). Plant communities include Mixed Grass Prairie, Sand Sage Shrubland, and Rhus trilobata (R. aromatica)/Yucca glauca/Hesperostipa comata shrublands. Clark's work (2001, 2014) at this unique site documents rare plants such as Asplenium adiantum-nigrum L. (G5S1), Apios americana Medik. (G5S1), and Aristida basiramea Engelm. ex Vasey (G5S2). Within the study area there are 46 species with a Great Plains distribution. Great plains species that occur at both White Rocks and the study area include Allium textile A.Nelson & J.F.Macbr., Asclepias engelmanniana Woodson, Asplenium trichomanes, Aristida basiramea, Buchloë dactyloides (Nutt.) Engelm., Delphinium carolinianum Walter, Eriogonum effusum Nutt., Mentzelia nuda (Pursh) Torr. & A.Gray, and Rosa arkansana Porter. Several shrubs appear at both sites, but Cercocarpus montanus characteristic of the hogbacks of the study area are absent from White Rocks. White Rocks includes populations of Prunus pumila L., absent at the study area.
Recent inventories of the Red Hill Study Area, (Heil Valley Ranch and Trevarton Open Space) (Vickery 2021), as well as Ron Stewart Preserve at Rabbit Mountain (Vickery 2021), both BCPOS parcels, demonstrate increased attention to the biodiversity of the neighboring foothills. Both parcels have a B1 ranking (outstanding biodiversity) from CNHP. The inventory of the Red Hill Study Area (320 acres) resulted in the documentation of 391 species. This parcel includes a portion of the 740-acre Trevarton property acquired by BCPOS in 2017. Infrequent or rare species documented by both the first author (who briefly explored the boundaries of this area) and Vickery include Claytonia rubra (Howell) Tidestr., Crepis atribarba A.Heller, Linaria canadensis (L.) Dum.deCours, Physaria bellii G.A.Mulligan, and Vicia Ludoviciana Nutt. ex Torr. & A.Gray. In addition, Vickery documented Asclepias stenophylla A.Gray, Carex oreocharis Holm, Lactuca ludoviciana (Nutt.) Riddell, and Orobanche multiflora Nutt. Vickery also documents local endemic Physaria vitulifera Rydb. at the site. Ron Stewart Preserve at Rabbit Mountain is located NW of the Study area, north of highway 66 in Longmont. His study documents 494 species (538 have been documented in total). This approximately 7000-acre parcel includes the southern extent of the hogbacks common in Larimer County to the north (Neid et al. 2008) Notable species present at both Rabbit Mountain and the study area are Aristida basiramea, Ceanothus herbaceous Raf., and Colorado endemics, Physaria bellii and Mentzelia speciosa Osterh.
There has been significant floristic work conducted north of the study area in Larimer County (Brune et al. 1996). In 2014 McAleer inventoried two parcels, Red Mountain Open Space (RMOS) and Soapstone Prairie Natural Area (SPNA), adding granular data to the 1996 and 2004 inventories by CNHP that delimited the significant biodiversity of Larimer County. These two parcels along the Wyoming border, were open to the public in 2009. SPNA is 18,728 acres, and was previously privately owned ranch land. West of SPNA is RMOS (14,980 acres), an ecotone between the foothills and the plains. Four-hundred-thirty-eight taxa were identified at these two parcels, compared to the study area where 381 species where documented. McAleer classifies 108 species with shortgrass prairie distributions, although species are often designated multiple affinities. Mentzelia speciosa (G3S3) was documented at SPNA and is also found at the study area. Cercocarpus montanus shrublands occur at RMOS, as well as occurrences of Hesperostipa neomexicana (Thurb.) Barkworth, for which there are only five records in Larimer County (SEINnet 2022). There are also five records for this species in two counties of Wyoming, the northern extent of its range.
Significant remnant grasslands and shrublands occur in the vicinity of Golden, CO in Jefferson County. This foothills transition zone south of the study area includes 556 acres of parkland. In 2020 CNHP surveyed 115 acres (Sovell et al. 2021) and documented 114 plant taxa. Rare species documented are: Physaria x1 (GNA/S1), Smilax lasioneura Hook. (G5/S3S4), Spiranthes diluvialis Sheviak (G2G3/S2). Tom Schweich has conducted ongoing botanical inventories of the area, making 835 collections as of 2020. Lorraine Yeatts has also contributed 334 collections. Significant parcels included in these inventories are North and South Table Mountain, Lookout Mountain, and North Washington Open Space. Cercocarpus montanus shrublands occur on North Table Mountain Park (1873 acres) which is owned and managed by Jefferson County Open Space. One-hundred-twenty-two species were documented at North Washington Open Space (4 acres) which includes a small remnant mixed grass prairie. Many taxa of interest are more common in the mountains and foothills and rare in the plains.
The September 2013 flood event impacted both parcels. This multi-state event was caused by a protracted period of heavy rainfall (September 11–12) and flooding (September 13–16). Water from flooded canyons traveled to the South Platte River in NE Colorado and Nebraska. Boulder and Larimer Counties were the most severely impacted. (Gochis et al. 2015) At Heil Valley Ranch, Geer Canyon Creek overflowed, causing flooding to Geer Canyon Drive. Riparian vegetation was damaged, in addition to roads and structures. (BCPOS 2016) At Hall Ranch, the flooded South St. Vrain Creek damaged the flood plain and Old South Saint Vrain Road (BCPOS 2022).
Before Euro-American settlement, many Ponderosa Pine ecosystems took the form of savannas which supported diverse understories (Matonis 2021). Subsequent changes in climate and human populations led to an increase in fire suppression and grazing. At lower elevations, Ponderosa Pine forests encroached on grasslands. These denser forests have a higher potential for high-severity fires leading to tree mortality, habitat loss for some plant species, and higher potential for an increase in non-native species. The last several decades have produced wildfires of an unprecedented size and scope. There have been six fires on Heil Valley Ranch between 1988–2020 (Addington et al. 2018; Matonis 2021). On October 17, 2020, the Calwood Fire burned a total of 10,106 acres, making it the biggest fire in the history of Boulder County. Approximately 4400 acres burned on Heil Valley Ranch. Sustained winds of 40 miles per hr caused high intensity fire for which much of the forest was unprepared. Many Pinus ponderosa 300–400 yr in age were lost (BCPOS 2021a; BCPOS 2021b).
Regeneration of Ponderosa Pine forest can be limited after severe fire and the success of post burn seedlings is dependent on climatic conditions (Addington et al. 2018). Affected portions of the study area may remain unforested for many years and it is possible that there will be a conversion of some areas from forest to grassland or shrubland. This change in habitat can also increase diversity and in turn create different patterns in the fire regime. Prescribed burns on the site have demonstrated potential to aid in the restoration of the Ponderosa Pine ecosystem (Matonis 2021).
Regional research indicates that increased richness and cover of exotic species is a risk following high severity fires (Fornwalt 2010; Matonis 2021). However, recent studies at Heil Valley Ranch have demonstrated that non-native species have so far not appeared in greater numbers than native species after the Calwood fire (Stevens-Rumann and Fornwalt 2021). In terms of other effects of high severity fires on the structure of plant communities, research following the Calwood Fire has shown burned sites to have higher proportions of forbs and lower proportions of graminoids and shrubs relative to unburned sites (Matonis 2021; Stevens-Rumann and Fornwalt 2021). Native grasses that declined at the site included Agrostis scabra Willd. and Muhlenbergia montana (Nutt.) Hitchc. New native forbs that appeared are Triodanis perfoliata (L.) Nieuwl. and Phacelia hastata Douglas ex Lehm. (Matonis 2021). There are only 20 herbarium records for Triodanis perfoliata in Boulder County (SEINet). These data considered variables, including management practices by BCPOS, such as thinning and prescribed burns, along with the variables of the fire itself. Long term monitoring supported by BCPOS enabled this research to take place. While these papers provide a short-term overview of the immediate effects of wildfire on local grassland and forest communities, continued research and monitoring is needed to determine the longer-term effects of wildfire.
This study provides comprehensive data on the flora of the North foothills of Boulder County. The purpose of this inventory is to provide a checklist of the flora of these substantial parcels that can be utilized by staff at BCPOS for conservation planning. Floristic inventories help to promote policy dedicated to the protection and restoration of natural resources and ecosystem services, which is especially relevant in an era of environmental change including forest fires that impacted this very area 2 yr after the inventory (in 2020). Floristic inventories have the potential to mitigate the biodiversity crisis by informing land management, conservation, and restoration. The legacy of land conservation by BCPOS and their continued efforts to understand and manage these landscapes, provides a model for other open space programs and conservation organizations.
The checklist is organized alphabetically by family, genus, and specific epithet. All collections made by the first author are deposited at the herbarium of the University of Colorado Museum (COLO). Nomenclature follows the Angiosperm Phylogeny Group III (2009). A total of 607 botanical specimens were collected. Bracketed entries include the collection numbers made by the first author. Sixty-five specimens were collected at the site prior to this study and are indicated by bracketed entries that include collector names and collection numbers. These collectors are Berta Anderson, Dina Clark, Tim Hogan, William Jennings, Judy King, Patrick Murphy, Richard Scully, Linda Senser, Stanley Smookler, William A. Weber, and Ron C. Wittmann. The most significant contribution was made by Dina Clark who added 32 specimens to the checklist. Seventeen of these specimens are the sole representatives of the checklist and the remainder add depth to the data presented.
Biogeographical affinities of plants from Heil Valley Ranch and Hall Ranch are parsed into the following categories: Africa (AFR), Circumboreal, Cosmopolitan, Eastern North America (ENA), Eurasia (EA), Europe (EU), Great Plains (GP), North America (NA), South America (SA), Southern Rockies (SORO), Southwest North America (SWNA), United States (US), Western North America (WNA), Western United States (WUS). We provide comments on the habitat and abundance of each species at the study area using the following rankings: abundant (>1000), common (>500), scattered (∼100), uncommon (<50), and rare (<25).
Chenopodium berlandieri Moq.
Uncommon in dry and disturbed areas. NA. 
Chenopodium pratericola Rydb.
Scattered in shrublands. NA. 
Chenopodium simplex (Torr.) Raf.
Uncommon in forested canyons. NA. 
Kochia scoparia (L.) Schrad.
Uncommon in disturbed grasslands. EA. 
Allium cernuum Roth
Common in Ponderosa Pine woodlands. NA. [249, 620]
Allium textile A.Nelson & J.F.Macbr.
Scattered in shrublands. GP. 
Rhus glabra L.
Scattered in open canyons and along road sides. NA. 
Rhus trilobata Nutt.
Abundant, a dominant component of shrublands. WNA. 
Toxicodendron rydbergii (Small ex Rydb.) Greene
Common on rocky slopes and canyon floors. NA.
Conium maculatum L.
Common in riparian areas. EU. 
Cymopterus acaulis Raf.
Scattered in forest openings. WNA. 
Harbouria trachypleura J.M.Coult. & Rose
Common in woodlands and forests. SORO. [126, 283], [Clark 4354]
Heracleum maximum W.Bartram
Uncommon. Found along montane canyon streams. NA. 
Lomatium orientale J.M.Coult & Rose
Common in grasslands and shrublands. GP. [285, 346]
Musineon divaricatum (Pursh) Nutt.
Scattered in shrublands. GP. 
Osmorhiza berteroi DC.
Uncommon, found in a cool montane ravine. NA (and South America). 
Apocynum androsaemifolium L.
Scatttered in shrublands and grasslands. NA. [Clark 4355]
Apocynum cannabinum L.
Common in shrublands and open woods. NA. 
Asclepias engelmanniana Woodson
Uncommon on grassland slopes. GP. 
Asclepias speciosa Torr.
Common in riparian areas. WNA. 
Asclepias viridiflora Raf.
Uncommon in dry grasslands. NA. 
Leucocrinum montanum Nutt. ex A.Gray
Scattered in grasslands. WUS. [274, 343]
Maianthemum racemosum (L.) Link
Uncommon in forests. NA. 
Maianthemum stellatum (L.) Link
Uncommon in forests. NA. [383, 548]
Yucca glauca Nutt.
Scattered on dry slopes. GP. 
Asplenium septentrionale (L.) Hoffm.
Rare. Found in rock crevices. WNA and EA. 
Asplenium trichomanes L.
Rare. Found in rock crevices. Cosmopolitan. 
Achillea millefolium L.
Common in woodlands and forest openings. NA and EA. 
Agoseris aurantiaca (Hook.) Greene
Uncommon, meadows and forest openings. WNA (and Quebec). 
Agoseris parviflora (Nutt.) D.Dietr.
Uncommon, woodlands. WUS. 
Ambrosia artemisiifolia L.
Scattered in disturbed areas and meadows. NA (and SA). 
Ambrosia psilostachya DC.
Common in disturbed areas and meadows. NA. 
Ambrosia trifida L.
Uncommon in disturbed mesic habitats. NA. 688
Antennaria anaphaloides Rydb.
Common in woodlands and forests. WNA. [366, 367, 418]
Antennaria parvifolia Nutt.
Scattered in woodlands and forests. WNA (and GP). 
Arnica cordifolia Hook.
Common in forests and along streams. WNA. 
Arnica fulgens Pursh
Scattered in meadows and rocky slopes. WNA. 
Artemisia frigida Willd.
Abundant in dry locations. NA (and EA). 
Artemisia ludoviciana Nutt.
Abundant in dry locations. NA. [243, 644]
Bidens frondosa L.
Uncommon, found in a stockpond. NA. 
Brickellia californica (Torr. & A.Gray) A.Gray
Scattered on dry, rocky slopes. WNA. [594, 651]
Brickellia eupatorioides (L.) Shinners
Scattered in dry habitats. NA. 
Brickellia grandiflora (Hook.) Nutt.
Scattered on rocky slopes. WNA (and GP). 
Carduus nutans L.
Scattered in fields and disturbed habitat. EA (and AFR). 
Centaurea diffusa Lam.
Scattered in disturbed areas, meadows and roadsides. EA (and Russia). 
Cichorium intybus L.
Scattered along roads and in disturbed habitat. EU. 
Cirsium arvense (L.) Scop.
Common in disturbed areas and fields. EA. 
Cirsium ochrocentrum A.Gray
Common in dry places. WNA and GP. [145, 480, 562]
Conyza canadensis (L.) Cronquist
Uncommon in disturbed fields. Cosmopolitan. 
Coreopsis tinctoria Nutt.
Uncommon in seasonal ponds. NA. 
Crepis atribarba A.Heller
Uncommon on tops of hogbacks. WNA 
Ericameria nauseosa (Pall. Ex Pursh) G.L.Nesom & G.I.Baird
Common in dry, open areas. WNA 
Erigeron divergens Torr. & A.Gray
Scattered in meadows and woodlands. WNA. 
Erigeron glabellus Nutt.
Scattered in wet areas. WNA (North). 
Erigeron speciosus (Lindl.) DC.
Scattered in ravines. WNA. [251, 709]
Erigeron subtrinervis Rydb. ex Porter & Britton
Uncommon along streams. WUS. 
Erigeron tracyi Greene
Common in meadows and woodlands. SWNA. 
Gaillardia aristata Pursh
Common in meadows and woodlands. NA. [224, 569], [Clark 4367]
Grindelia squarrosa (Pursh) Dunal
Common on dry slopes and ridges. NA. 
Gutierrezia sarothrae (Pursh) Britton & Rusby
Abundant in dry places. WNA. [256, 670]
Helianthus annuus L.
Common grasslands and fields. NA. [636, 658]
Helianthus pumilus Nutt.
Common in grasslands and rocky slopes. SORO. [219, 245]
Heterotheca foliosa (Nutt.) Shinners
Common in grasslands. WNA. 
Heterotheca villosa (Pursh) Shinners
Common in grasslands. WNA and GP. [137, 676]
Hieracium albiflorum Hook.
Scattered in open woodlands. WNA. 
Hieracium fendleri Sch. Bip.
Scattered in forests and woodlands. SWNA (and Central America). [563, 579]
Hymenopappus filifolius Hook.
Common in dry grasslands. WNA (and GP). 
Lactuca biennis (Moench) Fernald
Uncommon in forests. NA (North). 
Liatris punctata Hook.
Scattered in grasslands and meadows. NA (interi- or). [248, 639]
Nothocalais cuspidata (Pursh) Greene
Uncommon on ridgetops. GP. 
Packera fendleri (A.Gray) W.A.Weber & Á.Löve
Common in rocky slopes and forest openings. SORO. [406, 438]
Packera plattensis (Nutt.) W.A.Weber & Á.Löve
Scattered on dry slopes and grasslands. GP. 
Pseudognaphalium canescens (DC.) Anderb.
Scattered in grasslands and dry openings. WNA. 
Pseudognaphalium stramineum (Kunth) Anderb.
Scattered along streams. NA. 
Ratibida columnifera (Nutt.) Wooton & Standl.
Common in grasslands. NA. 
Rudbeckia laciniata L.
Common along montane streams. NA. 
Senecio integerrimus Nutt.
Scattered on open slopes. WNA and GP. [297, 411]
Senecio spartioides Torr. & A.Gray
Scattered in woodlands. WNA. [681, 685]
Solidago missouriensis Nutt.
Scattered in meadows and forests. NA. [598, 666]
Solidago simplex Kunth
Scattered in meadows. NA. 
Solidago speciosa Nutt.
Uncommon in riparian areas. ENA (and GP). 
Sonchus asper (L.) Hill
Scattered in in drainages. EA and AFR. 
Sonchus uliginosus M.Bieb.
Scattered in drainages. EA and AFR. 
Stephanomeria pauciflora (Torr.) A.Nelson
Common in grasslands and dry openings. SWNA [587, 641, 691]
Symphyotrichum falcatum (Lindl.) G.L.Nesom
Common in meadows and on roadsides. NA. [675, 689]
Symphyotrichum laeve (L.) Á. Löve & D.Löve
Common in meadows and forest openings. NA 
Symphyotrichum porteri (A.Gray) G.L.Nesom
Common in meadows and woodlands. SORO. [642, 652]
Thelesperma megapotamicum (Spreng.) Kuntze
Common in grasslands and open areas. NA. 
Townsendia grandiflora Nutt.
Common in woodlands and shrubland openings. GP. [158, 463], [Clark 4371], [Weber & Wittman 19490]
Tragopogon dubius Scop.
Scattered along trails and grasslands. EA. 
Xanthium strumarium L.
Uncommon, found in stock pond. NA. 
Berberis repens Lindl.
Common in the understory of forests and woodlands. NA. [293, 396]
Betula occidentalis Hook.
Dominant shrub along forested streams in Geer Canyon. WNA (North). 
Corylus cornuta Marshall
Common along forested streams in Geer Canyon. NA. 
Cynoglossum officinale L.
Uncommon introduced plant near drainages. EU. 
Hackelia floribunda (Lehm.) I.M.Johnst.
Common in woodlands and on dry slopes. WNA. 
Lappula occidentalis (S.Watson) Greene
Scattered in dry areas. NA. [201, 279]
Lithospermum incisum Lehm.
Common in grasslands and woodlands. NA. , [Clark 4365]
Lithospermum multiflorum Torr. ex A.Gray
Common in woodlands. NA (SORO and Mexico). [154, 233]
Mertensia ciliata (James ex Torr.) G.Don
Uncommon along streams in Geer Canyon. WUS. 
Mertensia lanceolata (Pursh) DC. ex A.DC.
Common in meadows and woodlands. WNA and GP. [122, 694]
Onosmodium bejariense DC.
Scattered in grasslands and dry woodlands. NA. 
Oreocarya virgata (Porter) Greene
Scattered in grasslands and forest openings. Endemic to CO and WY. [264, 362]
Phacelia hastata Douglas ex Lehm.
Common in grasslands and rocky slopes. WNA. [124, 416]
Alyssum simplex Rudolphi
Abundant in grasslands and low elevation slopes. EA and AFR 
Arabis pycnocarpa M.Hopkins
Scattered in meadows and forest openings. NA and E Asia. 
Barbarea vulgaris W.T.Aiton
Scattered in disturbed areas along drainages. EA and AFR. 
Boechera fendleri (S.Watson) W.A.Weber
Scattered in ponderosa pine woodlands. SWNA. 
Camelina microcarpa Andrz. ex DC.
Scattered along slopes of Dakota hogback. EA and AFR. 
Chorispora tenella (Pall.) DC.
Scattered along trails and slopes. EA. 
Descurainia incana (Bernh. ex Fisch. & C.A.Mey.) Dorn
Uncommon in forests. NA. 
Descurainia incisa (Engelm. ex A.Gray) Britton
Scattered in woodlands. NA 
Descurainia pinnata (Walter) Britton
Scattered in grasslands. NA. [Smookler 525]
Draba nemorosa L.
Uncommon in the understory of shrublands. NA and EA. 
Erysimum capitatum (Douglas ex Hook.) Greene
Common in understory of woodlands. NA. [284, 425]
Hesperis matronalis L.
Uncommon, found emerging from one drainage. EA and AFR. 
Nasturtium officinale W.T.Aiton
Common in drainages. Cosmopolitan. 
Noccaea fendleri (A.Gray) Holub
Uncommon on ridges. WNA. 
Physaria bellii G.A.Mulligan
Scattered on sandstone slopes. Endemic to Boulder and Larimer counties. SORO.
Physaria montana (A.Gray) Greene
Common in dry forest openings and rocky outcroppings. SORO. 
Sisymbrium altissimum L.
Scattered in grasslands. EU and AFR. 
Thlaspi arvense L.
Scattered in grasslands and disurbed areas. EA. [294, 695]
Turritis glabra L.
Common in forests and rocky slopes. Cosmopolitan. [334, 435], [Clark 4364]
Echinocereus viridiflorus Engelm.
Scattered in grasslands and rocky outcroppings. GP and Mexico. 
Opuntia macrorhiza Engelm.
Common in grasslands and understory of shrublands. NA (Great Plains, SWUS, Mexico). 
Opuntia phaeacantha Engelm.
Common in grasslands and understory of shrublands. SWNA. 
Pediocactus simpsonii (Engelm.) Britton & Rose
Scattered in woodland openings. SWUS. 
Campanula rotundifolia L.
Scattered in forests and woodlands. Circumboreal. 
Triodanis leptocarpa (Nutt.) Nieuwl.
Rare, one population found in grasslands. GP. 
Triodanis perfoliata (L.) Nieuwl.
Rare, found in woodlands. NA and SA. 
Celtis reticulata Torr.
Common on top of hogbacks and in box canyon. WNA. [164, 339, 692]
Humulus neomexicanus (A.Nelson & Cockerell) Rydb.
Uncommon in canyons. WNA. [469, 668]
Symphoricarpos occidentalis Hook.
Common in meadows and forests. NA. [207, 696]
Symphoricarpos rotundifolius A.Gray
Scattered in grasslands and rocky hillsides. WNA. 
Cerastium arvense L.
Common in forests and woodlands. Circumboreal. [125, 344]
Cerastium brachypodum (Engelm. ex A.Gray) B.L.Rob.
Scattered in drainages. , [Senser 302]
Dianthus armeria L.
Scattered in disturbed grasslands and woodlands. EA. 
Eremogone fendleri (A.Gray) Ikonn.
Uncommon along cliff tops. SWNA. 
Paronychia jamesii Torr. & A.Gray
Scattered on dry slopes and rocky outcroppings. SWNA. [240, 495], [Clark 4359]
Pseudostellaria jamesiana (Torr.) W.A.Weber & R.L.Hartm.
Uncommon in forests. WNA. 
Saponaria officinalis L.
Common in disturbed areas. EA. [196, 632]
Stellaria media (L.) Vill.
Uncommon in canyon streams. EA. 
Vaccaria hispanica (Mill.) Rauschert
Uncommon on dry grassland slopes. EA. 
Crocanthemum bicknellii (Fernald) Janch.
Uncommon, found on hogback west of Geer Canyon, previously burned by wildfire. ENA. [Scully 294]
Cleome serrulata Pursh
Scattered along roadsides. NA. 
Polanisia dodecandra (L.) DC.
Uncommon in sparse understory of grasslands. NA. 
Tradescantia occidentalis (Britton) Smyth
Common on dry hillsides. GP and SWNA. [150, 539]
Convolvulus arvensis L.
Abundant in grasslands and disurbed areas EA. 
Evolvulus nuttallianus Schult.
Scattered in old fields and dry grasslands. NA. (GP).  [Clark 4360]
Juniperus communis L.
Common forest shrub. Circumboreal. [308, 376]
Juniperus scopulorum Sarg.
Common on hillsides and forests. WNA. 
Carex brevior (Dewey) Mack. ex Lunell
Common along drainages. NA. [576, 167]
Carex hystericina Muhl. ex Willd.
Uncommon in drainages. NA. 
Carex inops L.H.Bailey
Abundant species of grasslands, dry woodlands, and forests. GP. [265, 316, 368, 521, 714]
Carex microptera Mack.
Scattered in forests. WNA. 
Carex nebrascensis Dewey
Common in drainages and depressions. WNA. [199, 441, 526]
Carex occidentalis L.H.Bailey
Uncommon in canyons. SWUS. [377, 566]
Carex petasata Dewey
Rare, found in seasonal pond. WNA. 
Carex scoparia Schkuhr ex Willd.
Scattered in seasonal ponds and streams. NA. [209, 500]
Cyperus schweinitzii Torr.
Uncommon in Pinus ponderosa savanna. ENA. [Clark 4461]
Eleocharis acicularis (L.) Roem. & Schult.
Uncommon, found in seasonal pond. Cosmopolitan. 
Eleocharis elliptica Kunth
Scattered in shrublands. NA (north of Mexico). 
Eleocharis palustris (L.) Roem. & Schult.
Abundant in drainages and moist meadows. Cosmopolitan. [170, 322, 513, 706]
Schoenoplectus acutus (Muhl. ex Bigelow) Á.Löve & D.Löve
Uncommon, found in seasonal pond. NA. 
Scirpus microcarpus J.Presl & C.Presl
Uncommon, found in drainages. NA. 
Scirpus pallidus (Britton) Fernald
Uncommon, in streams and wetlands. NA. [198, 606]
Athyrium filix-femina (L.) Roth.
Uncommon along canyon streams. Circumboreal 
Cystopteris fragilis (L.) Bernh.
Common in rocky places, including understory of shrublands. Cosmopolitan. [350, 379, 546]
Dryopteris filix-mas L. (Schott)
Rare, found in forested ravine. Circumboreal. 
Woodsia scopulina D.C.Eaton
Uncommon in rock crevices. NA. [430, 473]
Equisetum arvense L.
Common in drainages. Circumboreal. [442, 534]
Equisetum hyemale L.
Common in drainages. Circumboreal. [197, 446]
Arctostaphylos uva-ursi (L.) Spreng.
Common in forest understory. Circumboreal. [369, 680]
Pterospora andromedea Nutt.
Uncommon in forest understory. NA. 
Chamaesyce fendleri (Torr. & A.Gray) Small
Scattered in understory of shrublands. SWNA. 
Euphorbia brachycera Engelm.
Scattered in understory of shrublands and grasslands. SWNA. 
Euphorbia spathulata Lam.
Scattered on dry slopes. NA (and SA). 
Tragia ramosa Torr.
Common in grasslands and shrublands. SWNA. [165, 482], [Clark 4362]
Amorpha fruticosa L.
Uncommon in disturbed drainages. NA. 
Astragalus agrestis G.Don
Scattered in woodlands. NA (and EA). 
Astragalus drummondii Douglas
Scattered in grasslands. WNA. [159, 414]
Astragalus laxmannii Jacq.
Uncommon in moist meadows. WNA. 
Astragalus parryi A.Gray
Uncommon on rocky outcroppings. SORO. [275, 361]
Astragalus shortianus Nutt.
Uncommon on dry slopes. SORO. 
Astragalus tridactylicus A.Gray
Scattered on dry slopes. SORO. 
Dalea candida Willd.
Common in grasslands and shrublands. NA. [175, 498], [Clark 4361]
Dalea purpurea Vent.
Common in grasslands and shrublands. GP. [187, 550]
Glycyrrhiza lepidota Pursh
Scattered in streams and meadows. WNA. [450, 677]
Lotus corniculatus L.
Uncommon in disturbed areas. EA and NA. 
Lupinus argenteus Pursh
Scattered near streams and dry areas. WNA. 
Medicago lupulina L.
Naturalized plant, uncommon, near drainages. EU and AFR. 
Medicago sativa L.
Scattered in grasslands and disturbed places. EA. 
Melilotus albus Medik.
Common in disturbed areas. EA. 
Melilotus officinalis (L.) Lam.
Common introduced plant of disturbed areas. EA. 
Oxytropis lambertii Pursh
Common in dry rocky places. GP. [439, 629]
Oxytropis sericea Nutt.
Common in grasslands and woodland openings. WNA. [155, 282], [Clark 4356], [Anderson 1498]
Psoralidium tenuiflorum (Pursh) Rydb.
Common in grasslands. GP. 
Thermopsis divaricarpa A.Nelson
Common in shrubland and woodland openings. SORO. [299, 427, 515]
Trifolium repens L.
Common introduced clover in drainages and disturbed areas. EA. [171, 454, 634]
Vicia ludoviciana Nutt. ex Torr. & A.Gray
Uncommon. Occurring in understory of shrublands. SWNA. (Weber and Wittman 19492)
Frasera speciosa Douglas ex. Griseb.
Uncommon in forested canyons. WUS. [531, 559]
Gentiana bigelovii A.Gray
Uncommon. Scattered in meadows. WNA. 
Gentianella acuta (Michx.)
Uncommon in forest openings. NA. 
Erodium cicutarium (L.) L'Hér. ex Aiton
Common plant of grasslands and woodland openings. EA. 
Geranium caespitosum James
Common in grasslands and forests. SWNA. 
Ribes aureum Pursh
Scattered in lower grasslands and drainages. NA. 
Ribes cereum Douglas
Common in rocky outcroppings and dry hillsides. WNA. [191, 270]
Ellisia nyctelea (L.) L.
Scattered in Pinus ponderosa woodland. NA. [Hogan 5702]
Hydrophyllum fendleri (A.Gray) A.Heller
Scattered in drainages and ravines. WNA. [456, 467]
Iris missouriensis Nutt.
Scattered in wet meadows. WNA. [300, 324]
Sisyrinchium montanum Greene
Scattered in wet meadows and along streams. NA. [363, 409]
Juncus arcticus Willd.
Uncommon in cool ravines. Cosmopolitan. 
Juncus dudleyi Wiegand
Uncommon along canyon streams. NA. 
Juncus ensifolius Wikstr.
Scattered along canyon streams. WNA (and Canada), EU and East Asia. [554, 673]
Juncus interior Wiegand
Common in wet meadows and along streams. GP. [185, 359, 422, 131]
Schoenoplectus tabernaemontani (C.C.Gmel.) Palla
Uncommon along streams. Cosmopolitan 
Hedeoma hispida Pursh
Uncommon in rocky places. GP. [Clark 4464]
Marrubium vulgare L.
Common introduced plant in disturbed areas. EA and AFR. 
Mentha × piperita L.
Scattered in disturbed drainages. EA. , [Scully 308]
Monarda fistulosa L.
Common in wet meadows and woodland openings. NA. [208, 615]
Monarda pectinata Nutt.
Scattered in grasslands. SWUS. [354, 413]
Nepeta cataria L.
Scattered in disturbed areas and canyon floors. EA. [244, 595]
Prunella vulgaris L.
Common along streams. Cosmopolitan. 
Scutellaria brittonii Porter
Scattered in woodland openings. SORO. 
Teucrium canadense L.
Rare in moist drainages between hogbacks. NA. [Scully 310]
Calochortus gunnisonii S.Watson
Scattered in grasslands and shrublands. WNA (interior). [147, 477], [Clark 4368]
Prosartes trachycarpa S.Watson
Uncommon in cool ravines. WNA. 
Mentzelia nuda (Pursh) Torr. & A.Gray
Uncommon in disturbed grasslands. GP. 
Mentzelia oligosperma Nutt. ex Sims
Uncommon in bare soil of sparse grasslands. GP 
Mentzelia speciosa Osterh.
Uncommon on grassland slopes. SORO. 
Toxicoscordion paniculatum (Nutt.) Rydb.
Scattered in understory of grassland and shrublands WNA. 
Claytonia rosea Rydb.
Scattered in woodland openings. SWNA (interi- or). 
Claytonia rubra (Howell) Tidestr.
Uncommon but abundant at one site in open woodlands. WNA. 
Phemeranthus parviflorus (Nutt.) Kiger
Scattered in rocky grasslands and dry forest openings.GP. [440, 537]
Circaea alpina L.
Uncommon, found in cool forests. NA and EA. 
Epilobium brachycarpum C.Presl
Scattered in drainages and along streams. NA. [646, 663]
Epilobium ciliatum Raf.
Scattered in drainages and along streams. NA, SA and Asia. [556, 582]
Oenothera coronopifolia Torr. & A.Gray
Uncommon in understory of shrublands. SWUS. 
Oenothera curtiflora W.L.Wagner & Hoch
Scatterd in grasslands. NA. [489, 596]
Oenothera howardii (A.Nelson) M.E. Jones ex Prain
Uncommon in grasslands. SWUS. [341, 478]
Oenothera suffrutescens (Ser.) W.L.Wagner & Hoch
Uncommon along shale slopes. NA. [342, 357]
Oenothera villosa Thunb.
Scattered in disturbed areas. NA. [659, 722]
Corallorhiza maculata (Raf.) Raf.
Scattered in forests and woodlands. NA. [682, 711]
Goodyera oblongifolia Raf.
Rare. One population found in cool forested ravine. NA. 
Castilleja miniata Douglas ex Hook.
Scattered in wet meadows. WNA. [231, 626]
Castilleja sessiliflora Pursh
Scattered in grasslands. GP , [Clark 4370]
Orobanche fasciculata Nutt.
Uncommon on dry slopes, with Artemisia frigida. WNA. 
Orthocarpus luteus Nutt.
Uncommon in lower montane meadows. WNA. 
Argemone polyanthemos (Fedde) G.B.Ownbey
Common in grasslands and along roadsides. GP. [166, 487]
Corydalis aurea Willd.
Scattered in forests. NA. [289, 389], [Weber and Wittman s.n.]
Mimulus floribundus Lindl.
Rare. One population found growing along a narrow forest stream. WNA. 
Mimulus glabratus Kunth
Scattered along streams and disturbed drainages. NA. 
Pinus ponderosa P.Lawson & C.Lawson
Dominant pine in forests, woodlands, and savannas. WNA. 
Pseudotsuga menziesii (Mirb.) Franco
Common in lower montane forests. WNA. [433, 653]
Callitriche palustris L.
Rare. One population found in seasonal pond. Circumboreal(toSouthAmerica),[Murphys.n.]
Collinsia parviflora Lindl.
Common in forest and woodland openings. WNA. [296, 303]
Gratiola neglecta Torr.
Scattered in seasonal ponds and other moist areas. NA. [183, 514], [Murphy s.n.]
Linaria canadensis (L.) Dum. Cours.
Found in Pinus ponderosa savanna. NA. [Clark 4472], [Murphy s.n.]
Linaria dalmatica (L.) Mill.
Common noxious weed of grasslands. EA. [338, 707]
Penstemon secundiflorus Benth.
Scattered in grasslands and hillsides. SORO. [327, 356]
Penstemon virens Pennell ex Rydb.
Scattered in woodland openings. SORO. [127, 312]
Penstemon virgatus A.Gray
Scattered in understory of shrublands. SWNA. 
Plantago lanceolata L.
Scattered in disturbed areas.EA. 
Plantago major L.
Scattered along streams. EA. 
Plantago patagonica Jacq.
Uncommon in rocky outcroppings and dry meadows. NA (and SA). [168, 398]
Veronica anagallis-aquatica L.
Common in drainages and streams. Cosmopolitan. [212, 280]
Achnatherum hymenoides (Roem. & Schult.) Barkworth
Scattered in grasslands and shrublands. WNA. [215, 496]
Achnatherum lettermanii (Vasey) Barkworth
Uncommon grass of forest openings. WNA. 
Achnatherum robustum (Vasey) Barkworth
Scattered on dry slopes. SWNA. 
Achnatherum scribneri (Vasey) Barkworth
Scattered in grasslands and forest openings. SORO. [486, 565]
Aegilops cylindrica Host
Scattered along roadsides. EA. 
Agropyron cristatum (L.) Gaertn.
Abundant introduced plant of grasslands and roadsides. EA. 
Agrostis exarata Trin.
Uncommon in ephemeral pond. WNA. 
Agrostis gigantea Roth
Introduced plant of drainages and moist areas. EA. 
Agrostis scabra Willd.
Common grass in roucky outcroppings and meadows. NA (and Asia) [236, 701]
Agrostis stolonifera L.
Uncommon grass of ephemeral ponds. EA. [519, 524]
Alopecurus aequalis Sobol.
Common grass of moist places. Circumboreal. 
Alopecurus geniculatus L.
Uncommon introduced grass in moist places. EA. 
Andropogon gerardii Vitman
Common prairie grass. NA. [247, 591], [Clark 4466]
Aristida adscensionis L.
Uncommon bunch grass of dray and disturbed places. NA (to South America). [Senser 320]
Aristida basiramea Engelm. ex Vasey
Rare annual grass of barren places and rocky outcroppings. GP. [Clark 4469], [Scully 283]
Aristida purpurea Nutt.
Common grass of grasslands, shrublands, and woodland openings. WNA (and GP). [160, 568, 633, 698]
Bouteloua curtipendula (Michx.) Torr.
Scattered in grasslands. NA (to SA). 
Bouteloua gracilis (Kunth) Lag. ex Griffiths
Abundant of grasslands and shrublands. [253, 577, 699, 700, 721]
Bromus briziformis Fisch. & C.A.Mey.
Introduced grass. Scattered in disturbed woodlands openings. EA. , [Senser 282]
Bromus ciliatus L.
Uncommon grass of dry woodlands. NA. 
Bromus richardsonii Link
Uncommon grass of forests. WNA. 
Bromus squarrosus L.
Uncommon in disturbed areas. EU. [Senser 115]
Bromus tectorum L.
Dominant introduced grass at the study area. Present in most habitats. EA and AFR. [313, 423]
Buchloë dactyloides (Nutt.) Engelm.
Scattered in prairie dog towns and lower grasslands. GP. 
Dactylis glomerata L.
Common grass of disturbed areas and drainages. EA and AFR. 
Danthonia parryi Scribn.
Uncommon grass, found in lower montane meadow. SORO. 
Danthonia spicata (L.) P.Beauv. ex Roem. & Schult.
Common grass of meadows and forests. NA. [221, 523, 614]
Dichanthelium linearifolium (Scribn.) Gould
Scattered grass dry forest and rocky outcroppings. ENA. , [Clark 4462]
Dichanthelium oligosanthes (Schult.) Gould
Common in dry places. NA. [169, 518], [Clark 4369, 4470]
Echinochloa crus-galli (L.) P.Beauv.
Introduced grass. Scattered along roadsides. Asia and Africa. 
Elymus albicans (Scribn. & J.G.Sm.) Á.Löve
Common in woodlands and shrublands. WNA. [230, 329, 420]
Elymus canadensis L.
Scattered along streams and moist places. NA. [186, 544]
Elymus elymoides (Raf.) Swezey
Scattered in shrublands and dry places. WNA. [138, 483]
Festuca saximontana Rydb.
Common in forests and rocky slopes. NA. [388, 402, 475]
Glyceria grandis S.Watson
Uncommon along streams. NA. 
Hesperostipa comata (Trin. & Rupr.) Barkworth
Common in grasslands and shrublands. WNA. 
Hesperostipa neomexicana (Thurb.) Barkworth,
Common in grasslands and shrublands. SWNA. , [Clark 4353], [Senser 170]
Hordeum jubatum L.
Common along roadsides and in moist areas. NA (and Siberia). [182, 502]
Koeleria macrantha (Ledeb.) Schult.
Common grass of woodlands and savannas. NA (and EA). [226, 323]
Leucopoa kingii (S.Watson) W.A.Weber
Scattered in woodlands and forests. WNA. [229, 424, 590]
Leymus ambiguus (Vasey & Scribn.) D.R.Dewey
Scattered in woodlands and forests. SORO. [474, 703]
Leymus triticoides (Buckley) Pilg.
Uncommon along streams. WNA. 
Muhlenbergia alopecuroides (Griseb.) P.M.Peterson & Columbus
Common in shrublands and woodlands. SWNA (to SA). [189, 650, 672, 705], [Clark 4460, 4465, 4473]
Muhlenbergia montana (Nutt.) Hitchc.
Common grass of forests and woodlands. WNA (to Central America). [225, 508, 560]
Muhlenbergia paniculata P.M.Peterson
Uncommon grass of disturbed places. GP. 
Muhlenbergia racemosa (Michx.) Britton, Sterns & Poggenb.
Uncommon in disturbed drainages. NA. 
Muhlenbergia richardsonis (Trin.) Rydb.
Uncommon. Found in grasslands. WNA. 
Nassella viridula (Trin.) Barkworth
Scattered in grasslands and shrublands. GP. 
Panicum virgatum L.
Common in grasslands and shrublands. NA (and Central America). [607, 660, 683]
Pascopyrum smithii (Rydb.) Barkworth & D.R.Dewey
Common in grasslands and woodland openings. NA. [143, 173, 571, 630]
Phleum pratense L.
Common along streams. EA. [211, 532]
Piptatherum micranthum (Trin. & Rupr.) Barkworth
Scattered in the woodland understory. WNA. [161, 431], [Clark 4366]
Poa compressa L.
Abundant introduced grass. EU. [134, 390, 455, 465, 509], [Clark 4363]
Poa fendleriana (Steud.) Vasey
Scattered in forests and ravines. WNA. [390, 404]
Poa interior Rydb.
Uncommon grass of dry woodlands. NA. 
Poa pratensis L.
Abundant introduced grass. EA. [286, 348, 364, 400]
Poa secunda J.Presl
Uncommon grass flound in dry woodlands. WNA (and SA). 
Poa trivialis L.
Uncommon grass in wet meadow above drainage. EU. 
Poa wheeleri Vasey
Scattered in dry woodlands. WNA. 
Puccinellia nuttalliana (Schult.) Hitchc.
Uncommon grass of ephemeral ponds. NA. 
Schedonorus arundinaceus (Schreb.) Dumort.
Uncommon introduced grass. Found along trails. EU. 
Schedonorus pratensis (Huds.) P.Beauv.
Introduced grass. Found in disturbed areas. EA. [318, 453]
Schizachyrium scoparium (Michx.) Nash
Common prairie grass. NA. [252, 592], (Clark 4471)
Secale cereale L.
Uncommon grass of distrubed places. EA. 
Setaria verticillata (L.) P.Beauv.
Introduced grass. Scattered along roadsides. EU. 
Sporobolus compositus (Poir.) Merr.
Scattered in grasslands. GP. 
Sporobolus cryptandrus (Torr.) A.Gray
Common in grasslands. NA. [263, 589]
Vulpia octoflora (Walter) Rydb.
Uncommon grass, found in dry woodlands. NA. 
Aliciella pinnatifida (Nutt. ex A.Gray) J.M.Porter
Scattered in woodlands. SWUS. [314, 399]
Collomia linearis (Cav.) Nutt.
Scattered in woodlands. NA. 
Gilia ophthalmoides Brand
Uncommon, found along trail in forested area. WNA. 
Ipomopsis spicata (Nutt.) V.E.Grant
Uncommon in shrublands. WNA (interior) 
Eriogonum alatum Torr.
Scattered in grasslands and dry slopes. WNA. [152, 570]
Eriogonum effusum Nutt.
Common in grasslands and shrublands. GP. [259, 693, 717]
Eriogonum flavum Nutt.
Common in grasslands and shrublands. GP. , [Clark 4359]
Eriogonum umbellatum Torr.
Common on dry slopes and forest openings. WNA. 
Fallopia convolvulus (L.) Á.Löve
Uncommon vine of disturbed areas near trails, EA and AFR. [194, 631]
Persicaria hydropiper (L.) Opiz
Uncommon introduced plant of disturbed drainages. Cosmopolitan. 
Polygonum aviculare L.
Introduced plant found along roadsides. EA. 
Polygonum engelmannii Greene
Uncommon. Found in grasslands. WNA. 
Rumex acetosella L.
Common plant of disturbed woodlands. EA. [223, 664]
Rumex crispus L.
Common plant of disturbed wet areas. EA. 
Anagallis minima (L.) E.H.L.Krause
Uncommon, found in old quarry. Cosmpopolitan. (Murphy s.n.)
Androsace occidentalis Pursh
Uncommon, found in mosses of rocky outcropping. WNA. 
Androsace septentrionalis L.
Uncommon, found in cool forested ravine. Circumboreal. 
Dodecatheon pulchellum (Raf.) Merr.
Uncommon, found in canyon stream. WNA. 
Aconitum columbianum Nutt.
Uncommon along cool forest streams. WNA. 
Actaea rubra (Aiton) Willd.
Uncommon in forests. NA. [Jennings s.n.]
Anemone patens L.
Scattered in grasslands and woodlands. Circumboreal. [340, 371]
Aquilegia coerulea James
Uncommon in cool forested ravine. SORO. 
Clematis hirsutissima Pursh
Uncommon in woodlands. WNA. 
Clematis orientalis L.
Uncommon in disturbed drainages. EA. 
Delphinium carolinianum Walter
Scattered in shrublands. GP. 
Delphinium geyeri Greene
Common in grasslands and shrublands. SORO. [132, 488], [Clark 4357]
Ranunculus abortivus L.
Uncommon. Found along a cool forested stream. ENA. 
Ranunculus flammula L.
Uncommon in ephermeral ponds and quarries. Circumboreal. 
Ranunculus ranunculinus (Nutt.) Rydb.
Scattered along the forest edges. SORO. [301, 403]
Ranunculus uncinatus D.Don
Uncommon on in moist places. WNA. [King 3]
Thalictrum fendleri Engelm. ex A.Gray
Uncommon in shaded canyons. WNA. 
Amelanchier alnifolia (Nutt.) Nutt. ex M.Roem.
Scattered on cliffs, shrublands and grasslands. WNA. 
Cercocarpus montanus Raf.
Abundant, dominant component of shrublands. WNA. [269, 345, 567], [Clark 4467]
Crataegus succulenta Schrad. ex Link
Uncommon, found along roadsides. NA. 
Fragaria vesca L.
Scattered along canyon streams. NA. 
Fragaria virginiana Mill.
Scattered along forested streams. NA. 
Geum macrophyllum Willd.
Scattered along streams and wet meadows. Circumboreal. [238, 724]
Physocarpus monogynus (Torr.) J.M.Coult.
Common shrub of forests and rocky slopes. WNA. [128, 250, 330]
Potentilla fissa Nutt.
Scattered on rocky outcroppings and dry places. WNA. 
Potentilla hippiana Lehm.
Scattered in shrublands. SORO (WNA). 
Potentilla recta L.
Uncommon, found near trails. EA. 
Prunus americana Marshall
Scattered on slopes and along roadsides. ENA. 
Prunus virginiana L.
Common on rocky slopes and along drainages. NA. [325, 468, 603]
Purshia tridentata (Pursh) DC.
Common shrub of rocky outcroppings and dry places. WNA. , [Clark 4468]
Rosa arkansana Porter
Scattered in grasslands and shrublands. GP. [206, 336]
Rosa blanda Aiton
Common in woodlands and along streams. WNA. 
Rubus deliciosus Torr.
Common on cliffs and along forested canyons. SORO. [328, 555]
Rubus idaeus L.
Uncommon, found along narrow mossy streams. Circumboreal. 
Galium aparine L.
Introduced and common in woodlands. EA and AFR. [123, 291]
Galium boreale L.
Scattered in forests. Circumboreal. 
Galium triflorum Michx.
Scattered in forests. Circumboreal. 
Populus angustifolia James
Common in riparian areas. WNA. [479, 720]
Populus deltoides W.Bartram ex Marshall
Scattered in riparian areas. NA. 
Populus tremuloides Michx.
Scattered in canyons and lower montane areas. NA. 
Salix amygdaloides Andersson
Common along streams and moist places. NA. [444, 525]
Salix exigua Nutt.
Common along streams and drainages. WNA. [200, 447, 574]
Heuchera bracteata (Torr.) Ser.
Scattered on cliffs and in ravines. SORO. [437, 716]
Heuchera parvifolia Nutt. ex Torr. and A.Gray
Common on cliffs and in rock crevices. WNA. 
Micranthes rhomboidea (Greene) Small
Scattered on mossy slopes in forest openings. WNA. 
Scrophularia lanceolata Pursh
Common in drainages. NA. [195, 415]
Verbascum blattaria L.
Scattered in grasslands. EA and AFR. 
Verbascum thapsus L.
Abundant in most habitats. EA and AFR. 
Selaginella densa Rydb.
Scattered along rocky outcroppings and streams. WUS (and western Canada). [319, 382], [Clark 4459]
Selaginella weatherbiana R.M.Tryon
Uncommon on shaded sandstone outcrops in forests. SORO. [Scully 284]
Physalis hederifolia A.Gray
Scattered in disturbed places. SWNA. 
Physalis heterophylla Nees
Scattered in grasslands. ENA. 
Physalis longifolia Nutt.
Scattered in grasslands. NA. 
Typha latifolia L.
Common in lower elevation streams and drainages. Cosmopolitan. [599, 657]
Parietaria pensylvanica Muhl. ex Willd.
Scattered in the shade under ledges. NA. 
Urtica dioica L.
Scattered along streams and drainages. NA. [584, 621]
Verbena bracteata Lag. & Rodr.
Scattered in dry, disturbed places. Cosmpolitan. [516, 637]
Verbena hastata L.
Uncommon, found along lower drainages. NA. 
Viola canadensis L.
Common in woodlands and wet meadows. NA. [288, 349]
Viola kitaibeliana Roem. & Schult.
Scattered in grassy, rocky places. EU. [King 6]
Viola nuttallii Pursh
Common in woodlands and grasslands. GP. 
Viola pedatifida G.Don
Rare prairie violet, found in grasslands. GP. , [Scully 311]
This work would not have been possible without the support of the Boulder County Parks and Open Space program, in particular Claire DeLeo, Therese Glowacki, Kevin Grady, and Jennifer Kesler. We acknowledge generous support from COLO's collection managers Dina Clark, Tim Hogan, and James Ryan Allen. The first author thanks the Museum and Field Studies Department at CU Boulder for providing an avenue in which to pursue floristic research. She additionally thanks the members of her thesis committee: Erin Manzitto-Tripp, Jingchun Li, and Stephanie Mayer for their feedback and mentoring throughout this research project. She also thanks Philip Bentz and Isabel de Silva for their field contributions. We thank Jennifer Ackerfield, Carol English, and the Colorado Native Plant Society for providing training and sharing expertise about the Colorado flora. Clare Loughran at the University of California Botanical Garden provided direction and advice on publishing. The first author also thanks Katt Lissard and Lewis Warsh for encouragement and guidance throughout the research and publication process.