Descurainia pinnata (Walt.) Britt.

Tansy Mustard

Descurainia pinnata plant

Family - Brassicaceae

Stems - To +70cm tall, herbaceous, erect, typically multiple from stout taproot, branching above, dense glandular pubescent.

Descurainia pinnata stem

Leaves - Alternate, sessile, to +15cm long, 6-7cm broad, reduced upward, pinnate to deeply pinnatifid, pubescence simple, forked, or branching, also glandular. Leaflets typically pinnatifid. Leaf rachis channeled above.

Descurainia pinnata leaf

Inflorescence - Terminal raceme, very compact in flower, much elongating in fruit, to + 25cm long (tall). Flowers on short pedicels to 4mm long, typically glabrous. Pedicels elongating in fruit.

Descurainia pinnata inflorescenceInflorescence.

Flowers - Petals 4, yellow, -2mm long, 1mm broad, glabrous, spreading to recurving slightly at apex, obtuse at apex. Stamens 6. Filaments to 1.5mm long, yellow, glabrous. Anthers yellow, .2mm long. Ovary terete, subcylindric, 1mm long. Siliques to +/-1cm long, 2mm in diameter, subterete to 4-angled, many seeded. Seeds brown, 1mm in diameter. Fruiting pedicel to 1.5cm long.

Flowering - March - June.

Habitat - Waste ground, disturbed sites, open woods, prairies, glades, roadsides, railroads.

Origin - Native to U.S.

Other info. - This species is common in Missouri and can be found throughout the state. Another species, D. sophia (L.) Webb, which is introduced from Europe, is becoming common. The two can be distinguished by fruit size and leaf character.
I didn't get pics of the flowers of D. pinnata, but they are very close to those of D. sophia, so check out that page to see the flowers.

Photographs taken at Eagle Bluffs Conservation Area, Boone County, MO., 4-11-04.