As you begin making plans and starting seedlings for your fall garden, one you may want to consider is Brussels sprouts (Brassica oleracea). A member of the cole crops group (broccoli, cauliflower, collards, etc.), it is one of the more unique vegetables you can grow in your garden. It produces small cabbages in the leaf axils on a continually elongating central stem that can get over 3 ft. tall. The large blue-green leaves look a lot like collards. The leaves are edible and can be cooked just like collards.
Growing Brussels sprouts requires cool weather. A slow-growing, long-bearing crop, Brussels sprouts should be planted in late summer (8/15-10/15) for a crop that matures in the fall and winter. Brussels sprouts will continue to bear into spring until the weather gets too warm and causes the sprouts to become bitter. Brussels sprouts require 90 to 180 days to begin bearing after transplanting (depending on the variety) so it is a vegetable for the patient gardener. It takes 6-8 weeks to produce transplants. Like most vegetables, Brussels sprouts need a minimum of 6 hours of sunlight daily; more is better. They like fertile, well-drained, moist soils with plenty of organic matter. The soil pH should be on the high side of the range for vegetables, about 6.8, for optimum growth and to discourage clubroot disease. To be sure about pH, get the soil tested.
Brussels sprouts also need more boron than most other vegetables. Boron is a plant nutrient used in minute quantities by all plants; without it, Brussels sprouts develop hollow stems and small buds. If your plants have shown these symptoms, you can add boron to the soil by dissolving 1 level tablespoon of borax (such as 20 Mule Team) in 5 quarts of water and sprinkling it evenly over 50 square feet of bed. DO NOT be tempted to mix more, because too much causes problems. Also, do not apply unless your plants have shown the deficiency symptoms we just mentioned. Brussels sprouts get large, so they need to be about 18 to 24 inches apart in a row or bed. Water thoroughly after planting to encourage good growth. Mulch to keep the ground cool and moist. Water regularly, applying 1 to 1½ inches of water per week if plants don’t receive enough rain. Brussels sprouts require larger amounts of fertilizer than other cole crops. Before planting add about 0.5 lb of 13-13-13 per 30 square feet. Side-dress with about 0.5 lbs of calcium nitrate per 30 square feet about 4 weeks after planting, a second side-dress 4 weeks later, and a third side-dress 4 weeks after the second one.
Sprouts first form at the bottom of the plant and continue forming toward the top for several weeks. Brussels sprouts are ready to harvest when the tiny heads are firm, green, and 1 to 2 inches in diameter. Remove sprouts by twisting them until they break away from the plant. As you remove the lower sprouts, you can also remove yellowing leaves; the plant continues to grow upward, producing more leaves and sprouts. The plant will withstand temperatures into the 20’s. Sprouts usually taste sweeter after cold exposure. One full-sized, healthy plant can bear 2 to 3 pounds of sprouts. They come quickly at first but will slow down as the weather gets colder. Once a sprout is picked, new ones will not form in that spot. Full-grown sprouts keep well on the plant in cold weather, making them a great winter harvest item for gardeners in the South. Store fresh, unwashed sprouts in plastic bags in the refrigerator. Fresh sprouts taste best, though, so try to limit refrigeration to a day or two.
Insects that attack Brussels sprouts include harlequin bugs, cabbage loopers, diamondback moth, imported cabbageworm, cutworms, cabbage maggot, thrips, and webworms. Aphids can be especially difficult to control. The biggest insect problems with Brussels sprouts are aphids and caterpillars. Start inspecting your plants when leaves are 2-4 inches across.
Plants can also be bothered by several diseases including powdery mildew, downy mildew, black rot and clubroot. Choose resistant varieties and follow good sanitation. If you think you don’t like Brussels sprouts, try one of the many recipes out there such as caramelized Brussels sprouts and you just may be carving out a space in your garden to grow your own.
Dr. Joe Willis
Brussels sprouts growing in a Master Gardener demonstration plot.
The small cabbage-like sprouts form at the base of each leaf.