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Descurainia pinnata

western tansymustard

Brassicaceae western North America

Attracts Pollinators Drought Tolerant

Native to North America

SunFull Sun

WaterLow · drought-tolerant

Overview

Descurainia pinnata is an annual or winter annual in the mustard family (Brassicaceae), growing 8–30 inches (20–75 cm) tall on a single erect stem that branches in the upper half. The foliage is grayish-green and finely divided into narrow segments, densely covering the lower stem and becoming sparse toward the top. Small four-petaled flowers, pale yellow to cream and about 0.08 inch (2 mm) across, open in elongating racemes from spring into early summer. These give way to narrow club-shaped seedpods 0.2–0.5 inch (5–13 mm) long held on spreading stalks, each containing two rows of minute orange-brown seeds. The plant germinates with fall or winter moisture, forms a basal rosette, and bolts as temperatures rise. It grows across a wide range of dry, disturbed ground including desert flats, roadsides, overgrazed rangeland, and sandy washes. When tansymustard dominates spring forage, cattle and sheep grazing it heavily can develop neurological signs including impaired vision and tongue paralysis, a limitation in rangeland settings. Its short life cycle and heavy seed set let it colonize bare soil rapidly after disturbance.

Native Range

Descurainia pinnata is native to North America, occurring from southern Canada through the western and central United States into northern Mexico. It is most frequent in arid and semi-arid regions of the Great Plains, Intermountain West, and Southwest.

Suggested Uses

Descurainia pinnata is used in native revegetation and erosion control on disturbed dryland sites, where it stabilizes bare soil as an early colonizer. Its seeds and foliage feed seed-eating birds and small mammals. It is rarely grown ornamentally and is more often managed as a rangeland and roadside volunteer.

How to Identify

Identify Descurainia pinnata by its grayish-green, finely dissected leaves and slender erect stem 8–30 inches (20–75 cm) tall. The small pale yellow flowers, about 0.08 inch (2 mm) wide, are followed by narrow club-shaped pods 0.2–0.5 inch (5–13 mm) long on outward-angled stalks. The two rows of tiny seeds within each pod and the soft, often glandular-hairy foliage separate it from related tansymustards such as D. sophia, which has more thread-like leaf segments.

Appearance

Size & Dimensions

Height8" - 2'6"

Width/Spread4" - 1'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Spring

Flowering occurs from March through June, beginning earlier in low desert sites and later at higher elevations. The pale yellow racemes elongate as they bloom, with new flowers opening at the tip while pods develop below. Flowering lasts roughly 6 weeks on an individual plant before it sets seed and dies.

Detailed Descriptions

Foliage Description

grayish-green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 8.0(Neutral)

357912

Soil Types

sand loam rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Descurainia pinnata grows in full sun on sandy, gravelly, or loamy soils with sharp drainage and tolerates poor, low-nutrient ground. It needs little water once established, completing its cycle on winter and early-spring moisture. Seed germinates in fall or winter when soil is cool and damp, so sowing is timed to those conditions rather than to spring. As a self-seeding annual it needs no fertilizing or staking. In garden settings it can spread beyond its intended area through heavy seeding, so spent plants are often removed before pods shatter.

Pruning

No pruning is needed for this annual. Plants are typically pulled or cut at the soil line once flowering ends to limit self-seeding. Cutting before the pods turn tan and brittle prevents seed dispersal.