How to Plant, Grow, and Save Seeds from Brussels Sprout (Brassica oleracea)
These bite-sized greens are members of the species Brassica oleracea which includes broccoli, cauliflower, kale, and cabbage. They will flower and produce seeds in their second growing season after experiencing cold weather. Brussels sprouts are considered an advanced crop for seed savers.
Brussels sprouts require a long growing season. Plant Brussels sprouts seeds ¼” deep in flats 4-6 weeks before the last frost. Brussels sprouts seeds will germinate in 3-10 days. Transplant Brussels sprouts outside just before the last frost.
Brussels sprouts are susceptible to a handful of pests including cabbage butterflies, cabbage loopers, cutworms, flea beetles, harlequin bugs, and the diseases leaf spot and black rot. Many of the pests can be controlled by covering plants with row cover or by applying organic pesticides throughout the growing season.
Begin harvesting sprouts when the sprouts are firm and are approximately 1” in diameter. Mature sprouts will develop near the bottom of the plant first. Use a sharp knife to harvest individual sprouts as they mature.
Eating and Storing
There are many ways to prepare Brussels sprouts. The small leafy nodes can be eaten raw, cut thinly with a mandoline or a sharp knife and mixed with a light dressing for a fresh salad. They can be steamed or boiled and then simply dressed with butter, salt and pepper, and served as a side dish. Fresh Brussels sprouts will keep for several weeks in the refrigerator. If you’d like to stretch your enjoyment of Brussels sprouts into the winter, this vegetable can be blanched and frozen.
Brussels sprouts are a biennial crop. Biennials typically do not flower in their first growing season. They must first experience cold weather before they flower, set seed, and die in their second growing season.
When saving seeds from Brussels sprouts, separate varieties by at least 800 feet in their second year. To ensure viable seeds, save seeds from at least 5 plants. To maintain a variety over time, save seeds from between 20-50 plants.
To save seeds from Brussels sprouts, first decide how you will vernalize your plants. Vernalization can happen in the field or in storage. Overwinter Brussels sprouts in the field if you will have 10-12 weeks of cool weather (around 50 °F) without regular temperatures below 35 °F.
When plants cannot be successfully overwintered in the field, they can be vernalized in storage. Before the first frost, dig up the entire plant, roots and all. Replant Brussels sprout plants into containers filled with slightly moist potting mix or sand. Then, find a place to store your plants. The optimum storage conditions for Brussels sprout vernalization ranges from 34-39 °F and 80-95% relative humidity. A traditional root cellar is ideal but garages, sheds, and other unheated structures work well in some climates.
In the spring, when the soil can be worked, replant Brussels sprouts in your garden. Space plants at least 36” apart. Staking the plants is recommended to support talk seed stalks. After flowering and producing seed pods, pods will become dry and turn brown as the seeds inside also mature and brown. As with many of the Brassica crops, the window of time for an optimal harvest may be short as mature pods will begin to shatter and bird predation can become a problem.
Gather seeds by cutting entire branches or by harvesting whole plants. Because of this species’ tendency to shatter, the harvested material should be placed on drop cloths or in containers to prevent seed loss. Thresh branches of mature fruit by rubbing the pods between your hands or by flailing the brittle pods against any surface that will cause fruits to break open.
Store Brussels sprouts seeds in a cool, dark, and dry place in an airtight container to keep out moisture and humidity. Properly stored Brussels sprouts seeds will remain viable for several years.