Brassica nigra (L.) W.D.J. Koch
Sinapis nigra L.
Black mustard is native to tropical North Africa, temperate regions of Europe, and parts of Asia. It is naturalized throughout most of North America. Black mustard prefers disturbed soils, river or stream floodplains, lake shores, and meadows and fields. The plant contains glucosinolates, chemicals that deter herbivores.
Plants: 24-96" (60-243 cm) tall, branching sometimes. Stems are smooth near the top, become sparsely to densely hairy near the base. They are covered with a waxy substance that rubs off easily.
Flowers: Yellow, with four petals, in clusters at stem tips. Each petal is ¼-⅜" (7-11 mm) long and ¹/₁₆-⅛" (3-4 mm) wide.
Fruits: Long narrow upward-pointing seedpods are ⅜-⅞" (1-2.5 cm) in length. Each seedpod contains four rounded black or brown seeds.
Edibility: Black or dark brown seeds are commonly used, after removing seed coats and grinding, as a curry spice or similar flavoring agent.
Medical: Mustard or other pastes made from the seeds were once used to treat respiratory ailments or relieve muscular pains.
Brassica nigra at Illinois Wildflowers
Brassica nigra on gobotany.nativeplanttrust.org
Brassica nigra on Wikipedia
Brassica nigra from the Jepson Manual
Brassica nigra description by Thomas H. Kent, last updated 6 Aug 2019.