The California Phenology Thematic Collections Network (CAP TCN) is a collaborative project that seeks to maximize the value of herbarium specimens and their data, especially for understanding changes in plant phenology due to anthropogenic climate change. The project unites personnel in herbaria at California universities, research stations, natural history museums, and botanic gardens with the goal of capturing images, transcribing label data, and producing georeferenced coordinates of nearly one million preserved plant specimens collected over the past 150+ years. Each digitized specimen will also be scored for its phenological status—the stage of growth and reproduction of the specimen such as flowering or fruiting. The CAP TCN is developing efficient workflows and data standards necessary to collect, store, and analyze trait data from specimens to ensure their utility for research and other applications. These novel resources and data will enable powerful research in phenology and other topics in the California Floristic Province biodiversity hotspot and beyond.

Carduus cinereus M.Bieb. populations have been discovered in the Hells Canyon Wilderness of northeastern Oregon and western Idaho. These plants were initially identified as C. pycnocephalus L. They are distinguished from that species by loosely clustered, usually pedunculate, heads and by scarious-margined phyllaries. These plants are genetically distant from other North American Carduus species (<94% similarity) based on DNA sequence comparisons of the internal transcribed spacers between the 18S and 26S nuclear rDNA regions. Carduus cinereus is new to North America. A revised key to the species of Carduus in North America is presented.

Dicentra uniflora Kellogg (Papaveraceae), a small, single-flowered, ephemeral geophyte, was studied at three main and several secondary forest sites at the southern end of the Cascade Range in California (2009–2018). Emergence was closely linked to snowmelt, with flowering to senescence taking six to seven weeks, at elevations ranging from 1350–2575 m. Plants transitioned from flowering to fruit maturation within three weeks. Percent seed set in this perennial was high, ranging from 81–93% over five sites; seeds per fruit ranged from 44–83. In 2018, weekly field observations quantified the fate of flowers on plants staked when flowers appeared: only 27–43% of the flowers produced mature fruits with seeds, 23–24% dried up, and 25–30% disappeared, often leaving the pedicels. Black-tailed deer are suspected to be the primary herbivore, although nocturnal larvae of the butterfly Parnassius clodius, known to consume Dicentra leaves, may also be responsible at higher elevations. Each seed bears an easily-dislodged elaiosome, but little of the expected seed dispersal by ants was seen throughout the study. Field plantings of seeds illustrated that germination can occur in winter, below the snow, with seedlings bearing only a single cotyledon emerging from the ground in the spring. A seedling quickly produces a tiny food-storing, belowground bulblet before disappearing with the summer drought of the Mediterranean-type climate. The second-year plant produces a new bulblet and sometimes a tiny tuber, but only a single leaf, and plantings in the field suggest that it may take up to 10 years or more before an individual reaches flowering stage. A flowering plant has one or two fusiform tubers approximately 21 mm long and a cluster of ∼9 whitish bulblets approximately 4 mm long. Published research in the closely-related D. cucullaria (L.) Bernh. indicates that bulblets are undeveloped food-storage leaf bases unique to four species of Dicentra, capable of giving rise to small plants and providing food for plant development. Bulblets planted in this field study clearly indicate they are capable of asexual reproduction. As in some other geophytes, dry weight of D. uniflora tubers was significantly greater in June at the beginning of the summer drought than in November when the plants began renewed root growth early in the fall wet season. The depth to the tops of tubers on plants occurring in clusters varied from 3.2–10.7 cm in the rocky, loamy or sandy-loamy soils of these sites.

Blue oak woodlands in California have been a focus of conservation concern for many years. Numerous studies have found that existing seedling and sapling numbers are inadequate to sustain current populations, and recent work has suggested that blue oak woodlands might be particularly vulnerable to a warming climate. California has recently experienced a drought of historically unprecedented severity, resulting in the mortality of tens of millions of trees, including an apparent spike in mortality in oak communities. Here we present the results of a survey of tree mortality and composition in blue oak woodlands in Sequoia National Park. We found that 18% (95% CI = 14–24,) of all standing trees and 23% (95% CI = 17–30) of standing Quercus douglasii Hook. & Arn. (blue oak) were dead, substantially higher than proportions of dead trees recorded in pre-drought datasets, which showed 4% (95% CI = 2–9) standing dead for all trees and 5% (95% CI = 4–7) dead or 8% (95% CI = 4–16) standing dead for blue oak. Furthermore, much of this mortality appeared to be recent. Based on foliage or fine twig retention, 19% (95% CI = 14–26) of blue oak and 23% (95% CI = 16–31) of Quercus wislizeni A. DC. (interior live oak) appear to have died recently. In contrast, only 5% (95% CI = 3–8) of Aesculus californica (Spach) Nutt. (California buckeye) and 5% (95% CI = 2–11) of Fraxinus dipetala Hook. & Arn. (California ash) appear to have died recently. Even after such high mortality, with blue oak basal area dropping by 26% (from 9.5 m²/ha [95% CI = 7.4–11.6] to 7.0 m²/ha [95% CI = 5.3–8.7]), blue oak remains the dominant species in these ecosystems. However, given the lack of recruitment and the apparent vulnerability to extreme drought, blue oak populations may be at risk for severe decline if such mortality events become more frequent.

Silene nelsonii M.R. Mesler, M.S. Mayer, and S.K. Carothers (Caryophyllaceae), a species with large, day-blooming flowers from the Trinity River Basin of northwestern California, is described and illustrated. In the past, plants assignable to this new species have been referred to incorrectly as S. bolanderi A.Gray or S. hookeri Nutt. subsp. bolanderi (Gray) Abrams, names that rightfully apply to another member of the Silene hookeri complex. Here we argue that both S. nelsonii and S. bolanderi are worthy of recognition as separate species based on morphological distinction and a molecular phylogenetic analysis. Silene nelsonii differs from S. bolanderi by its more deeply lobed, white petals; lack of well-developed coronal petal appendages; densely ciliate petal bases; and shorter, sometimes branched sepal hairs. We present a key to the five members of the S. hookeri complex, all of which are in some degree rare in California and worthy of conservation concern.