Chorispora tenella (Pall.) DC.

Blue Mustard

Chorispora_tenella_plant.jpg
STATS

Introduced
CC = *
CW = 5
MOC = 8

© 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.

Chorispora_tenella_stem.jpg 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.

Chorispora_tenella_leaf1.jpg Leaf adaxial.

© SRTurner

Chorispora_tenella_leaf2.jpg Leaf abaxial.

© SRTurner

Chorispora_tenella_leaf2a.jpg Leaf abaxial surface.

© SRTurner

Chorispora_tenella_leaves.jpg Pressed leaves.

© DETenaglia

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

Chorispora_tenella_inflorescence.jpg Inflorescence.

© SRTurner

Chorispora_tenella_inflorescence2.jpg 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.

Chorispora_tenella_flowers.jpg Flowers.

© SRTurner

Chorispora_tenella_flower.jpg Flower.

© SRTurner

Chorispora_tenella_sepals.jpg Sepals.

© SRTurner

Chorispora_tenella_corolla.jpg 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.

Chorispora_tenella_fruit.jpg 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).