E-Flora BC: Electronic Atlas of the Flora of British Columbia

Descurainia pinnata (Walter) Britton
western tansy mustard
Brassicaceae (Mustard family)

Introduction to Vascular Plants

© Virginia Skilton  Email the photographer   (Photo ID #25534)

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Distribution of Descurainia pinnata
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Descurainia pinnata ssp. brachycarpa

Species Information

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Annual herb from a taproot; stems 10-60 cm tall, simple or branched above, sparsely hairy, multibranched, often stalked-glandular above.
Basal and lower stem leaves once or twice pinnately lobed, linear to egg-shaped, hairy, 3-10 cm long; upper stem leaves once pinnate to almost entire, generally glabrous, rarely glandular, 1-10 cm long.
Racemes elongate; flower stalks 6-12 mm long, at about 45 degrees to axis of inflorescence; petals yellow, erect, 2-3 mm long, exceeding sepals by about 0.5 mm; sepals 1.5-2.5 mm long.
Siliques, somewhat thicker towards the tips, rounded above, about as long as or shorter than the stalks, 7-12 (15) mm long; styles short, not beaklike; seeds 1-20 per chamber, partially in 2 rows, about 0.8 mm long.
Two highly variable, and often intergrading, varieties occur in our region.

1. Siliques 4-12 mm long, usually nearly equal to or longer than the stalks....................... ssp. intermedia (Rydb.) Detl.

1. Siliques 10-20 mm long, usually shorter than the stalks.................. ssp. filipes (A. Gray) Detl.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Dry shrublands and waste places in the montane and steppe zones; common in S BC, S to E WA, CO, NV and E CA.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Descurainia pinnata

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 283 721 1685
Slope Gradient (%) 0 40 90
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
25 188 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 2 5
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BG(41), BWBS(2), ESSF(1), IDF(19), MS(1), PP(15), SBS(5)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Taxonomic and Nomenclatural Links

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General References