Brussels sprouts are a large, slow‐growing, cool‐weather crop. Plant seedlings in July for harvest in fall and winter. The sprouts become sweeter after the first frost. They are hardy to frosts and light freezes. They are an excellent source of vitamins A and C. Brussels sprouts are a member of the brassica family and should be planted in an area that has not grown other brassicas (cabbage, kale, broccoli) for at least one year.
Brussels sprouts do best in full sun, at least six hours of direct sun. It thrives in rich well drained soil with a pH between 6.0‐7.5. Mix in a shovel full of composted manure, granular all purpose fertilizer, and lime to each planting hole.
Brussels sprout seedlings can be planted in April and May for summer harvest. Seeds can be started indoors under lights in February and March.
Brussels sprouts for fall harvest need to mature before fall frosts begin. Seeds should be started 100‐115 days before the first frosts. Therefore, by late June seeds should be started in flats indoors under lights or outdoors in the Portland area. Transplant seedlings to the garden when they are four weeks old. Starts can be planted July through mid August. Since Brussels sprouts prefer cooler temperatures, choose an area in the garden that may be partially shaded by larger summer crops.
Brussels sprouts will grow quite large, so space them 18‐24” apart in rows 24‐40” apart. You can interplant your Brussels sprouts with fast growing crops, such as lettuce or cilantro to make productive use of your garden space and to help shade the small sprout seedlings. Cover your new planting with floating row cover to prevent attacks from cabbage loopers and other chewing insects.
How much water your plants will require depends on the soil and weather. Water new transplants daily, or when the top 2” of the soil is dry. Once they reach 12” Brussels sprouts need average, evenly moist soil. Avoid overhead irrigation, instead use drip or flood irrigation or hand watering.
Brussels sprouts are heavy feeders, and benefit from a side dressing of composted manure or all purpose granular fertilizer two weeks after transplanting. Repeat side dressing once a month for the next two months.
You can boost sprout size, but reduce quantity, by removing the top growing point once sprouts have formed on the bottom 12”. This can also be done when the harvest slows to help redirect energy to sprout development. Remove the bottom leaves if they turn yellow.
As a sprout begins to swell, remove the leaf just under it. This will channel energy into the sprout development.
Brussels sprouts are harvested from the bottom of the stalk up. Continuously pick summer sprouts when they are marble size. If you want to harvest all at once instead of continuously, pinch the top of the stalk off 4‐ 8 weeks before intended harvest date. When harvest time arrives, cut off entire stalk 1” above ground level.
Fall sprouts are harvested when they are 1‐2” across and firm. Use a sharp knife to remove the sprouts and lower leaves. You can also harvest all at once by cutting the entire stalk 1” above ground level. Store entire stalk in root cellar, cool basement, or garage. Brussels spouts will store 3‐5 weeks when kept at 32°F.
Many problems that can occur with Brussels sprouts are due to weather and cultural conditions. Plants will bolt in reaction to hot weather and drought. Correct planting time, moderate and consistent moisture, soil amending, and row covers are all strategies to improve growing conditions.