Spotted knapweed (Centaurea stoebe) and brown knapweed (Centaurea jacea) are members of the Asteraceae and natives of Eurasia. Centaurea stoebe is a major invasive species in North America, dominating large stretches of grassland. It also is known to form hybrids in North America with closely related naturalized Centaurea spp., including C. jacea. Both species were introduced on Nantucket Island, a coastal island 44 km south of Cape Cod, Massachusetts, and morphologically unusual, possible hybrid populations have been reported. The aim of this study was to test for hybridization between these weeds in an isolated setting. Chloroplast marker sequences revealed that all the hybrid-like plants shared the same haplotype with C. jacea populations. The analysis of nuclear markers with microsatellite markers showed surprisingly little intra- and inter-specific gene flow between populations and no evidence of hybridization between C. stoebe and C. jacea. Two populations with hybrid-like morphology are most likely environmental plastic morphs of C. jacea.

A new hybrid of the autumnal daffodils Narcissus serotinus and N. deficiens is described for the first time from Seville Province (southern Spain). Seven qualitative characters and 21 quantitative measurements were taken from the hybrid and progenitors. Intermediate and uniparental characteristics were detected. The description of N. xhispalensis enlarges the list of wild hybrid daffodils in the Iberian Peninsula, the center of speciation for Narcissus.

Inula racemosa is reported as new to Canada, with occurrences in Ontario and Québec. It is also reported as new for several states in the United States. It was first reported for North America in 2020, based on a 2017 collection in Vermont. Earlier collections from Québec (2004) and Michigan (2014) were subsequently found, however. Its distinctive appearance led to the identification of additional records on the web page iNaturalist, the postings often initially misidentified as the common I. helenium. Almost two dozen North American occurrences are now known from Illinois, New Hampshire, New York, Ontario (the largest cluster of occurrences), Québec, Washington, and Wisconsin. Several of these populations contain hundreds to thousands of plants. All populations are considered to likely be of recent origin. At least some represent escapes from cultivation for medicinal or ornamental purposes. Inula racemosa may show a preference for calcareous substrate and river shore sites in the wild. It does not appear to have substantial potential to be invasive into native plant communities.

Hiking trails provide the opportunity for people to access, experience, and appreciate natural areas, but they also pose the risk of damage by converting vegetated areas to trail, providing the opportunity for off-trail hiking, and increasing soil compaction. To assess the impact of hiking trails on the plant community of a northeastern forest ecosystem, trail width was measured, and understory vegetation was documented at the trail edge, 3 m from the trail, and 5 m from the trail every 4 km along the Northville–Placid Trail from Benson to Averyville Road in the Adirondack State Park of New York State in August 2018. Soil compaction, canopy cover, and the tree species in the canopy were documented, including from the trail itself. The mean trail width was 65.18 ± 6.06 cm. Within the 183.39 km of trail sampled, 119,533.60 ± 11,113.43 m² of forest were replaced with trail. Soil compaction was greatest in the trail and significantly lower off the trail. None of the canopies of the tree species was more likely to occur away from the trail than adjacent to or directly above the trail. Canopy cover did not differ significantly among sample locations. Cover of understory species was not significantly different near to or away from the trail. Species richness in the understory was significantly higher adjacent to the trail than 5 m from the trail, but trail width, canopy openness above the trail, canopy openness adjacent to the trail, and soil compaction were not significantly related to species richness adjacent to the trail. Understory community composition was more similar among plots within a sample location than between plots 5 m from the trail at adjacent sample locations. Collectively, the plant community outside of the trail itself is not significantly affected by the presence of the trail. The major impact of the trail is the loss of the plant community at its margins as the trail width increases. Hikers should be further educated and encouraged to use trails in ways that minimize the width of the trail to protect the ecosystem, along with trail managers continuing to increase the sustainability of the trail design.

A previously described but unnamed hybrid of Geum aleppicum and G. canadense is reported from central New York, Vermont, and southern Ontario. Wild plants were compared to a cultivated plant and all exhibited traits intermediate in characters between the parent species. Comparative analysis of floral characters showed little relationship to Geum virginianum, as previously proposed. The hybrid is also compared to two similar hybrids involving G. urbanum, with which it might be confused. The hybrid is described and named here as G. xhainesianum, nothosp. nov. A key to Geum species and hybrids east of the Rocky Mountains is presented.