With branching stems up to 30 inches tall, this common Eurasian weed bursts into bloom in late winter and produces thousands of seeds before fading with the summer heat. Clusters of small, yellow flowers with 4 petals in a cross pattern cover the branch tips. Note the upper fruiting capsules overtop the flower clusters, the capsules are longer and wider than its stalk (pedicel), and the pinnate leaves have only 2–6 pairs of lobes with the end lobe the largest. Foliage is hairless to sparsely hairy.

FLOWER: February–May. Rounded clusters of small, yellow flowers with 4 petals, each 1/8 inch long (3 mm), forming a cross; flowering stem elongates as seed capsules (siliques) mature; capsules just below the flower cluster curve upward and overtop the flowers. Capsule a narrow cylinder 1 1/4–2 inches long (3–5 cm) on a stem (pedicel) 1/4–3/8 inch long (6–10 mm); pedicel is noticeably shorter and thinner than the capsule; mature capsules spread away from the stem and angle upward.

LEAVES: Basal with a petiole (stalk), but not clustered in a tight rosette; alternate on stem, upper blades similar but smaller than basal leaves. Leaves pinnately lobed, oblong in outline, 1–5 inches long (3–12 cm) with 2–6 pairs of lobes and one larger lobe at the tip. Upper leaves sometimes unlobed.

HABITAT: Sandy, loamy, rocky soils of fields, pastures, roadsides, disturbed areas; desert grasslands and scrub, pinyon-juniper woodlands, riparian areas.

ELEVATION: 3,600–6,100 feet.

RANGE: Widespread, naturalized throughout SW: AZ, CA, CO, NV, NM, TX, UT.

SIMILAR SPECIES: Tall tumble mustard, S. altissimum, nearly statewide except SE plains, blooms in the summer and has fruit with stout pedicels as wide as the capsule, the upper fruit capsules do not overtop the flowers, and the upper leaves have narrow, linear lobes. Flixweed, Descurainia sofia, also with long cylindric fruiting capsules, has leaves with fern-like divisions.

NM COUNTIES: Widespread southern half NM, scattered in northern NM in low-elevation, disturbed habitats: Bernalillo, Catron, Chaves, De Baca, Dona Ana, Eddy, Guadalupe, Grant, Hidalgo, Lea, Lincoln, Luna, Otero, Rio Arriba, Roosevelt, San Juan, Sandoval, Sierra, Socorro, Taos, Valencia.