Flower:

Small densely packed rounded clusters at the end of branching stems that elongate as the plant matures. Flowers are about 1/3 inch across, with 4 rounded bright yellow petals and 6 greenish stamens with yellow tips in the center.

Leaves and stem:

Leaves are up to 6 inches long and 2½ inches wide, deeply divided into narrow to angular lobes, the tip lobe largest and triangular to arrowhead shaped, with 2 to 4 pairs of lateral lobes that often point backwards. Leaves are hairy, with irregular, coarse teeth around the edges, and stalked, becoming smaller and shorter stalked as they ascend the stem. Stems are covered in spreading to downward pointing (deflexed) hairs, especially in the lower plant and may be hairless near the flowers.

Fruit:

Fruit is a very slender pod ¾ to 1½ inches long, spreading to upward curved, with the brown stub of the style at the tip.

Notes:

A weed of landscapes, nurseries and waste places this species has become more common in the metro in recent years. We suspect it is a lot more widespread than the herbarium records indicate. The yellow mustards can be difficult to distinguish as the flowers all look much the same. Tall Hedge Mustard is most easily distinguished by the triangular terminal lobes on the leaves, hairy stem, and spreading pods. A similar species is Hedge Mustard (Sisymbrium officinale), which has shorter (less than ¾ inch) more erect fruit, and flowers less than ¼ inch across.