Field Mustard

Field Mustard is direct-sown or set out as transplants in full sun, in soils ranging from sandy to heavy clay and tolerating a wide pH range, though it performs best in well-drained, moist, fertile ground. It withstands drought, moderate heat, and low-fertility soils, and while it grows best in full sun it will also tolerate moderate shade. In regions such as North Carolina it is commonly sown in mid-summer to mature as a fall crop, and its frost-hardy, annual habit allows it to be planted for cool-season harvest.

Field Mustard is attacked by a range of common brassica pests, including aphids, whiteflies, flea beetles, and caterpillars such as cabbage loopers, cutworms, and beet armyworms, along with slugs and snails. Disease problems include club root, white rust, leaf spot, and rots such as damping-off and bacterial soft rot.

Caution: the roots, leaves, and especially seeds contain sulfur compounds called glucosinolates that can irritate the digestive tract or cause thyroid problems in livestock, particularly horses, if consumed in quantity over time, producing symptoms such as colic, diarrhea, anorexia, excessive salivation, and thyroid enlargement.

Roots are best harvested at about two inches in diameter, and their flavor improves after exposure to frost. Insufficient water, lack of fertilizer, or delayed harvesting can cause the roots to turn woody, and if left in the ground the plants will bolt and flower the following spring.

Culinary: Both the root and the leaves of Field Mustard are edible raw or cooked; young leaves are used in salads while older leaves are typically sautéed.

Cover crop: Field Mustard is grown as a winter annual or rotational cover crop in vegetable, specialty, and row-crop systems, valued for rapid fall growth, high biomass production, and nutrient scavenging. When its biomass is incorporated into soil, sulfur compounds break down into isothiocyanide, giving it use as a biofumigant that can help suppress nematodes, soil-borne diseases such as damping-off, and weeds; it can be grown alone or mixed with other brassicas, small grains, or legumes, and has also been interseeded between rows of cash crops such as chili peppers and sweet corn without affecting their yields.

Forage: Cultivars with larger roots, known as forage turnip, have been grown as livestock feed in Europe and Asia for at least 600 years and remain useful for extending the fall grazing season for dairy cows and other livestock, though care is needed because of the glucosinolate content described above.

Field Mustard is native to Eurasia and has become naturalized across much of North America after long cultivation in Europe and Asia as a forage and vegetable crop. Its horticultural forms, including turnip, rapini, and related leafy types, trace back to this same widespread Eurasian ancestor rather than to a single, more recent domestication event.