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Tansy Mustard

Descurainia pinnata

Photo © by Michael Plagens

Photographed at Vulture Peak, Maricopa Co., Arizona, USA. March 2008.

LEAVES: Leaves are thrice - or more - pinnately divided. Ultimate segments are almost minute.

leaf of tansy mustard, Descurainia pinnata

This photo from a plant at South Mountain in Phoenix. Resting on the leaf is a very small fly which could be a kind of leaf miner, f. agromyzidae.

ANNUAL: One or a few tall leafy stems exceptionally reaching one meter tall. A spring annual; few plants last beyond May in the Sonoran Desert.

RANGE: Frequent throughout the Sonoran Desert in Arizona and Mexico on hillsides and along better watered canyons. In drought years tansy mustard does not germinate. Beyond Arizona this plant is widely distributed throughout much of North America with a number of subspecies and varieties recognized.

FRUIT: Oblong capsules can vary considerably in size from 4 mm to 2 cm with corresponding variance in number of seeds.

FLOWERS: Flowers are small and may be cream or yellow; not very showy except for an occasional plant with many flowers open at once. Again the usual mustard flower morphology of 4-4-6.


This is one of the mustard species used as a food plant by the caterpillars of Sara Orange-tip butterflies (Anthocharis sara).

Brassicaceae -- Mustard Family

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Copyright Michael J. Plagens, 1999-2010