

Mountain Tansymustard Descurainia incana
Mountain Tansymustard is an annual wildflower native to Alaska, Canada, and the lower 48 states. It blooms May – Aug. A host for pollen-specialist native bees.
More about this plant
Descurainia incana is a species of flowering plant in the mustard family known by the common name mountain tansymustard. It is native to much of North America, including most of Canada, the western United States, and Baja California. It is known from many types of habitat. It is a biennial herb with a slender, greenish, often hairy stem sometimes exceeding a meter tall. The leaves are narrowly to widely oval in shape, the lower ones lobed and sometimes compound, the upper generally unlobed. The mustardlike inflorescence is a series of developing fruits beneath an elongating cluster of small bright yellow flowers. The fruit is a thin, pointed silique up to 2 centimeters long. Wikipedia →
Growing & care
USDA PLANTS · TRY- Hardiness
- ≥ zone 4 derived from its U.S. range
- Lifespan
- Annual
- Foliage
- Broadleaf
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 · 1 bee visitor
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.
1 native & managed bee species is documented visiting Mountain Tansymustard :
How we know this (1) 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.
Sources for this entry (23) 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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