Black mustard plants (Brassica nigra) are native to the coastal regions of the Mediterranean Sea in southern Europe and belong to the same plant family as cabbage and horseradish plants. Black mustard plants are grown for both their edible leaves and seeds, which are slightly stronger and spicier than brown mustard seeds. The black mustard plant can grow up to 8 feet tall with tiny yellow flowers and wide leaves. You can grow black mustard plants in your garden in the cooler springtime months.
Plant your black mustard plants in early spring, right after the last frost. Select a planting site that receives full to partial sunlight and has rich, fertile soil.
Dig planting holes that are the same depth as and twice the width of the nursery containers. Work into the soil some rich, organic compost.
Space your black mustard plants about 6 inches apart. If you're planting black mustard seeds, cover them loosely with 1/2 inch of soil. Plant the black mustard plants at the same depth as they were planted in the nursery containers.
Water your black mustard plants lightly every other day to keep the soil evenly moistened. Water directly onto the soil and avoid getting water on the plant leaves.
Feed your black mustard plants once every two weeks with a liquid all-purpose plant fertilizer, according to the instructions on the label. You can also top-dress the soil around the plants every two weeks with 1 or 2 inches of organic compost.