Chorispora tenella (Pall.) DC.

Blue Mustard

© SRTurner

Family - Brassicaceae

Habit - Taprooted annual forb.

Stems - Spreading to erect, to 40 cm, branched from the base and above, with stalked glands usually mixed with sparse, unbranched hairs.

	Stem and node.
© SRTurner

Leaves - Alternate and basal, mostly short-petiolate, 3.0-8.0 cm long, sparsely covered with stalked glands (rarely also a few unbranched hairs), not clasping, the leaf blades oblanceolate to lanceolate or narrowly elliptic, shallowly and broadly toothed, those of the lower leaves less commonly deeply pinnately divided.

	Leaf adaxial.
© SRTurner

	Leaf abaxial.
© SRTurner

	Leaf abaxial surface.
© SRTurner

	Pressed leaves.
© DETenaglia

Inflorescence - Loose racemes terminating branches, the lower branches subtended by reduced leaves, glandular pubescent.

	Inflorescence.
© SRTurner

	Inflorescence.
© SRTurner

Flowers - Sepals 4-6 mm long, narrowly ascending, linear-lanceolate, sparsely covered with stalked glands. Petals 6-10 mm long, clawed, spreading after calyx tube, purple to bluish purple. Stamens 6, the anthers yellow. Styles minute or absent at flowering, becoming elongated as a beak as the fruit matures. Ovary terete, 6 mm long, 0.7 mm in diameter, glabrous.

	Flowers.
© SRTurner

	Flower.
© SRTurner

	Sepals.
© SRTurner

	Corolla
© SRTurner

Fruits - Siliques, ascending and curved upward, 3.0-5.0 cm long, linear, circular in cross-section, usually somewhat constricted between the seeds, the tip with a tapered beak 1-2 cm long, the valves lacking well-defined midnerves, not dehiscing, but breaking transversely into 2-seeded segments, usually with stalked glands. Seeds in 1 row in each locule, embedded in the thick, corky fruit-wall, 1.4-1.6 mm long, broadly ovate-elliptic in outline, flattened, the margins not winged, the surface smooth to minutely roughened, greenish yellow.

	Fruit.
© SRTurner

Flowering - April - June.

Habitat - Railroads, disturbed areas.

Origin - Native to Asia.

Lookalikes - None.

Other info. - At present this plant is uncommon in Missouri, known from only a few scattered locations. It is far more common in states to our west. It is unusual among Missouri's mustards in having bluish petals rather than the much more common yellow. This feature, along with the stalked glands, which are fairly conspicuous under close examination, and the long, round fruits make for an unambiguous identification.

Photographs taken off Highway 9, Platte County, MO., 4-15-00 (DETenaglia); also at Fort Robinson State Park, Dawes County, NE, 5-9-2025 (SRTurner).