How to Plant, Grow, and Save Seeds from Mustard (Brassica juncea, Brassica nigra, Brassica hirta)

Mustard can be grown for its edible leaves or its aromatic seeds. Mustard generally produces seeds in its first year of life. Prolific and pungent, this cool-weather crop will grow well in crisp spring and fall weather.


Mustard seeds can be sown anytime after the last frost of the season. Sow seeds either early in the spring after danger of frost or in the early fall after the summer’s heat has passed. Sowing too late in the spring or during summer months will cause early bolting and excessive spiciness. Seeds will germinate in 4-10 days. Leave 12” between plants.

Mustard can suffer heavy pressure from flea beetles, especially in the spring. Protect plants with row cover or use an organic pesticide to repel beetles.

Mustard greens can be harvested throughout the growing season, though their punch and pungency increases in intensity as they mature. When growing mustard to use its seeds as a spice, wait until the seed pods have turned brown and seeds are fully mature before harvesting.

Eating and Storing

When grown to full size, mustard greens are quite pungent and are thus typically cooked or pickled. Baby greens, on the other hand, have a delicate flavor and are are often eaten raw in salads. Mustard greens do not last long in storage after harvest. Place them in a bag to slow dehydration and eat greens within a few days of picking.

Saving Seeds

Mustard is an annual crop. It will complete its full life cycle, including germination, reproduction, and death, in one growing season.

When saving seeds from mustard, separate varieties by 800 feet to ½ mile. You only need to plant five mustard plants in order to harvest viable seeds. To maintain a variety over time, save seeds from between 20-50 plants.

At maturity, seed pods dry and turn light brown. The mature seeds they contain can be light brown, reddish brown, or dark brown. Depending on the size of the plants at flowering, and on the seed quantity desired, seeds can be gathered by cutting off individual branches or by harvesting whole plants. Seeds are easily lost during harvest and drying as the capsules shatter. To prevent seed loss, the harvested material should be placed on drop clothes or in containers. If weather conditions allow, harvested plants can be spread out on breathable fabric and left in the garden to dry. Plants should be allowed to dry until the seeds become too hard to dent with a fingernail.

Branches can be threshed by rubbing the fruits between one’s hands or against any surface that will cause the pods to break open. The seeds and chaff can then be screened and winnowed to clean the seeds.

When stored under cool, dry conditions, mustard seeds can be expected to remain viable for six years.