Plant · P-190

Black Mustard

Brassica nigra

Black mustard is a fast, spicy leaf and seed crop - the source of traditional brown mustard - but it's also one of the most allelopathic plants in cultivation, its phytotoxins strong enough to clear competing plants from a bed outright. Its seed can stay viable in the soil for up to fifty years, so it must always be cut, grazed or turned into the soil before it flowers into seed - one missed cutting can tie up a patch of ground for a working lifetime. It doubles as a fast green manure, ready in about eight weeks, and its mustard-oil compound is the same one used in commercial cat and dog repellents. Its seed and pods are toxic to livestock in quantity, so it belongs in a contained bed, never a grazed pasture or near a drainage where seed could wash away.