Vegetable · Brassicaceae
Brussels Sprouts
Brassica oleracea Gemmifera Group
Plant them for fall and let a light frost do the rest, and the sprouts come in firm and sweet.
Full sun
Every 3–7 days
41–77°F · 5–25°C
80–110 days
Overview
Brussels sprouts are a cool-season member of the cabbage family, the same species as broccoli, kale, and cauliflower, all coaxed into different shapes by generations of growers. The plant builds a tall, sturdy stalk studded with dozens of little cabbage-like buds, and those buds are the sprouts you eat. It is a biennial grown as an annual, harvested in its first season long before it would ever flower.
This is a crop that rewards patience. Brussels sprouts grow slowly and need a long stretch of cool weather to do their best, so gardeners time them to mature in fall rather than the heat of summer. Cold actually improves them, turning starch to sugar so the sprouts taste sweeter after the first light frosts.
They ask for steady care over a long season: rich soil, even moisture, and protection from the cabbage pests that find every brassica in the garden. Get the timing right and feed them well, and a single stalk hands you weeks of harvest from the bottom up.
Care
The short version: full sun and rich, evenly moist soil, planted so the sprouts mature in cool fall weather, with steady feeding through a long season and a sharp eye for cabbage pests.
Light
Brussels sprouts want full sun, ideally 6 or more hours a day, to build the strong stalk that carries a heavy crop. They tolerate a little partial sun, but real shade gives you weak plants and loose, disappointing sprouts.
Water
Keep the soil evenly moist all through the long season, around 1 to 1.5 inches (2.5 to 4 cm) of water a week. A swing between bone dry and soaking stresses the plant, so mulch to hold moisture and keep the roots cool.
Soil
Plant in rich, well-drained loam loaded with organic matter, since these are hungry plants that stay in the ground for months. Aim for a pH between 6.0 and 7.0, and lean toward the higher end, which also helps hold clubroot at bay.
Temperature
Brussels sprouts are a cool-weather crop that runs best from about 41°F to 77°F (5°C to 25°C). Hardened plants shrug off frost and stand in the garden until temperatures fall toward 20°F (-7°C), and that cold is what sweetens the sprouts.
Humidity
Ordinary outdoor humidity suits them, so there's no number to chase. Good airflow matters more than moisture in the air, since crowded, damp foliage invites the diseases that trouble brassicas.
Feeding
These are heavy nitrogen feeders. Work a balanced fertilizer into the bed at planting based on a soil test, then start side-dressing with nitrogen about 3 to 4 weeks after transplanting and feed through the growing season to keep the plant pushing out sprouts.
Pruning
Strip off the lower leaves as they yellow and the sprouts beneath them mature, working your way up the stalk. About 3 to 4 weeks before you want to harvest, you can pinch out the growing tip to drive energy into the remaining sprouts so they size up evenly.
Size & spacing
A mature plant stands 2 to 4 feet (60 to 120 cm) tall and spreads about as wide. Set transplants 18 to 24 inches (45 to 60 cm) apart so air moves freely between the big leaves and disease stays down.
When to plant
Brussels sprouts are built for the back half of the year. Start the seeds in late spring, set the plants out in early to midsummer, and harvest from early fall into winter, picking the firm sprouts from the bottom of the stalk upward as the cold sweetens them.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Sow indoors 6-8 weeks before transplanting; in cold-winter regions sow in late spring (May-June) so plants mature as a fall crop, or 4-6 weeks before the last spring frost for an early planting
- Plant: Transplant hardened seedlings in early to mid summer (late June-early July in northern gardens) for fall harvest; in mild-winter regions plant in late summer for winter harvest
- Harvest: Harvest from early fall into winter, picking firm 2.5-4 cm sprouts from the bottom of the stalk upward; flavor sweetens after light frosts and plants can stand in the garden until temperatures drop toward 20°F
Hardiness
USDA hardiness zones: 2–9
Temperature: down to -46°C
Troubleshooting
Most Brussels sprouts trouble traces back to timing, feeding, or the steady pressure of cabbage-family pests. Catch the early signs on the leaves and roots and you can usually keep a problem from spreading up the stalk. Match what you see below, then act while it still helps.
Plants wilt in the heat and the roots are swollen
Clubroot is a soilborne disease of cole crops that thrives in acidic, wet ground, and it shows up as wilting on warm days and stunted growth. Dig up a struggling plant and you'll find the telltale swollen, club-shaped galls on the roots. There's no cure once it takes hold, so destroy infected plants roots and all, lime the bed toward pH 7.0, and move your brassicas to clean ground.
Fix:
- Remove and destroy infected plants including roots; do not compost them
- Lime soil toward pH 7.0 or slightly above to suppress the pathogen
- Move brassicas to a clean bed
Loose, leafy sprouts that never tighten up
Blown, open sprouts almost always come from heat rather than anything wrong with the soil. When the buds form in summer warmth instead of cool fall weather, they grow loose and leafy, and a late dose of nitrogen makes it worse. Shift your planting so the sprouts mature in the cool of fall, and top the plant 3 to 4 weeks before harvest to firm up what's left.
Fix:
- Time plantings so sprouts develop in cool fall weather
- Harvest loose sprouts promptly and use them; they remain edible
- Top the plant 3-4 weeks before harvest to firm up remaining sprouts
Powdery gray aphids packed into the sprouts
Cabbage aphids build up fast on brassicas in warm weather and tuck themselves deep between the sprout leaves where they're hard to reach. Watch for dense, mealy gray colonies on the leaf undersides, curled foliage, and sticky honeydew. Blast them off with a hard spray of water, then treat the undersides thoroughly with insecticidal soap or horticultural oil and pull any badly infested lower leaves.
Fix:
- Knock colonies off with a strong spray of water
- Apply insecticidal soap or horticultural oil with thorough coverage of leaf undersides
- Remove and destroy heavily infested lower leaves
Ragged holes in the leaves with green droppings below
Three caterpillars do this damage, and they often work together: the imported cabbageworm, the back-arching cabbage looper, and the small, wriggling diamondback moth larva. Flip the leaves and check for green caterpillars and frass, and watch for the white butterflies that lay the cabbageworm eggs. Handpick what you find, spray Bt or spinosad while the caterpillars are still small, and cover the plants with floating row cover to shut the moths out.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) or spinosad while caterpillars are small
- Cover plants with floating row cover to exclude egg-laying moths and butterflies
Toxicity
Good news for pet owners: Brussels sprouts are a food crop and safe to grow around cats, dogs, and other animals. The plant is not toxic, and the worst a curious nibble brings is a bit of gas. Cook them before serving to people, since a steady diet of large raw amounts is the only real catch.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe to be around. A curious cat that chews a leaf might get a little gassy, but nothing in the plant will harm it.
Dogs None
No real concern here. Dogs that bolt down a big serving of raw sprouts may end up flatulent or briefly unsettled in the stomach, and that's the worst of it.
Horses None
Not toxic to horses. Brassica greens can be a bit gassy in quantity, so treat them as an occasional nibble rather than a staple.
Rabbits None
Fine for rabbits in small amounts. Introduce the leaves slowly, since a sudden load of any cabbage-family green can loosen their digestion.
Livestock None
Cattle, goats, and sheep can graze brassica foliage without trouble at normal levels. Only steady, heavy raw feeding raises any concern.
Birds None
Backyard hens happily peck at the leaves and trimmings with no ill effect.
People Safe
Grown to be eaten and good for you. The sprouts are best cooked, and only a chronic diet of large raw amounts would matter for thyroid health.
No special handling precautions; wash before eating as with any garden produce.
Varieties
Brussels sprouts come in a handful of dependable varieties, from old heirlooms to colorful modern hybrids. These are the ones worth knowing by name.
Long Island Improved
A classic open-pollinated heirloom on a fairly compact plant that was the standard home-garden sprout for generations.
Jade Cross E
An early hybrid that handles heat well and yields heavily, which makes it a good bet where the fall season runs short.
Falstaff
A late variety with red-purple sprouts that keep much of their color through cooking.
Companions
Brussels sprouts do best beside plants that mask their scent from cabbage pests, and worst beside a few crops that simply don't get along with the cabbage family.
Plant near
onions: WVU Extension lists the onion family as compatible with cabbage-family crops; alliums' strong scent helps mask brassicas from common pests
aromatic herbs (sage, rosemary, peppermint): WVU Extension lists aromatic herbs such as sage, peppermint, and rosemary as compatible with the cabbage family; their scents help confuse and deter cabbage pests
beets: WVU Extension lists beets as compatible with cabbage-family crops; the low-growing roots share space well beneath tall brassicas
Keep apart
strawberries: WVU Extension lists strawberries as incompatible with cabbage-family crops and recommends keeping them apart
How to propagate
Brussels sprouts are grown from seed, started indoors and moved out as transplants once they're big enough to hold their own.
SeedEasy
Sow indoors 6-8 weeks before transplanting (late spring in cold-winter regions for a fall crop); seeds can also be direct-sown about 4 months before the expected first fall frost · Germinates in about 5-10 days; seedlings reach transplant size in 4-6 weeks
Brussels sprouts come up easily from seed. Sow about a quarter to half an inch (0.6 to 1.3 cm) deep in sterile starting mix 6 to 8 weeks before you plan to transplant, and the seedlings break ground in 5 to 10 days and reach planting size in 4 to 6 weeks. Harden them off, then set them out 18 to 24 inches (45 to 60 cm) apart at the same depth they grew in their pots.
Myths
Brussels sprouts must be hit by a hard freeze before they are worth harvesting.
The plant doesn't need a freeze at all, and any firm sprout is ready to pick. Cool fall weather and light frosts do sweeten the flavor by building up sugars, which is why the crop is timed to mature in fall. You can still harvest fine, tight sprouts well before the first frost.
Cutting the top off a Brussels sprouts plant ruins the crop.
Topping is actually a recommended trick, not a mistake. Pinching out the growing tip 3 to 4 weeks before harvest stops the plant climbing and pushes its energy into the sprouts already on the stalk so they fill out more evenly.