Black Mustard (Brassica nigra) and its close relative, Field Mustard (Brassica rapa) have a long history in medical Herbalogy going all the way back to the ancient Greeks. The Romans were Mustard enthusiasts and most assuredly carried its seeds throughout Europe onward to the island of Brittan. The colonists and the later immigrants of the New World have done likewise for North America.
Description: Yellow flowers blooms from June to October. They are found in a four petal, cross-counter configuration growing above seed pods which will contain the desirable seeds. The whole plant can grow to 4 feet and beyond with the lower stalked leaves are lobed and roughly toothed. Higher leaves tend to be more lance shaped. Wild Field Mustard (Brassica rapa) is very similar to Black, but differs mainly by having stalkless lower leaves. These leaves tend to surround the stem with lateral lobes. Seeds fruit from June to October.
Location: Both have been naturalized to the USA shores and can be found coast to coast with the exception of an area between central Montana and northwestern Minnesota, engulfing all of North Dakota and upper part of South Dakota.
Parts Used: The seeds which are encapsulated in the pods contains the volatile oils. I consider the tincture of the entire plant, including the leaves, of use in formulating liniments, washes, and poultices.
Medicinal Uses: An irritant, stimulant, tonic, appetite stimulant, diuretic, and emetic as described by M Grieve in her 1931 text, A Modern Herbal. The mustards have a long history in Herbal medicine being utilized in poultices and plasters. Counterirritation is most likely the mechanism which brings relieve when mustard is applied to deep seated congestions and pain. Hot water washes using the bruised seedpods have long been useful as medicinal body bathes. American Indians were said to bruise the mustard leave for a toothache and headache remedy. The mustard plant can be infused into various oils or lard to produce a counterirritant salve for external applications