Sierra Tansymustard Descurainia californica
Sierra Tansymustard is an annual wildflower native to the lower 48 states. It blooms Jun – Aug. A host for pollen-specialist native bees.
More about this plant
Descurainia californica is a species of flowering plant in the family Brassicaceae known by the common name Sierra tansymustard. This plant is native to western North America from California to Wyoming. It is a resident of varied habitats from mountain forest to sage scrub. This spindly mustardlike plant has a single thin stem which branches and may reach over half a meter in height. Its sparse leaves are divided into two to four pairs of dull green lobes each one to six centimeters long. The tiny bunched flowers at the tip of each stem are bright yellow. The fruit is a tiny podlike silique on a straight pedicel. Pedicels holding fruits stick out from the stem at intervals. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 6 derived from its U.S. range
- Lifespan
- Annual
- Foliage
- Broadleaf
- Flower colour
- Yellow AI AI image-analysis of community-science photos (~87% expert agreement) — not a botanical record
Wildlife & pollinators
How pollinator value is scored →❧ Caterpillar hosts ~3 caterpillar species
Descurainia supports ~3 caterpillar species.
Native butterfly & moth caterpillars are the base of the terrestrial food web — most songbirds rear their young almost entirely on them. As a host for native Lepidoptera this is a modest genus.
Recorded feeding on Descurainia in North America, including:
✦ Bees specialist-bee host
Specialist native bees depend on it.
Some native bees are pollen specialists (oligolectic) — they raise young only on pollen from particular plant genera. Descurainia is a recorded specialist-bee host, so losing it can mean losing the bee that relies on it.
Related plants
More Descurainia →
How we know this (2) Methods & honest limits
We take the plant’s U.S. county range and look up each county’s long-term climate, then summarise: native rainfall = the median annual rainfall across its counties; heat tolerance = the warm end (90th percentile) of average temperature across its range (mirroring how our cold-hardiness floor uses an extreme). Counties + medians blunt the roadside/observer bias that makes point-level climate unreliable. Needs at least five placeable counties.
Honest limits: A realized, sampling-biased niche (where it has been recorded, not its physiological optimum), and county climate is coarse — large Western counties span deserts and mountains. Derived guide, never a measured fact.
McKenzie et al. assigned each species a flower colour with a GPT-4V vision model over iNaturalist photos. We use the confident tier plus a separately-labelled lower-confidence top-up (mostly inconspicuous green/brown flowers), and render it as a small tint — never as an asserted fact, and kept out of the written synopsis.
Honest limits: AI image inference (~87% expert agreement on the confident tier); a decorative, confidence-tiered indicator, not a measured trait.
Sources for this entry (20) Open & cited
Cite this page Open data, please attribute
PlantKey’s data is open under CC BY-SA 4.0 — free to reuse and adapt, with attribution and the same licence. Photos keep their own per-image licence + credit (see Sources above).
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