Vegetable · Brassicaceae
Brussels Sprouts
Brassica oleracea Gemmifera Group
Plant for fall and let a light frost finish the job, 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, each selected into a different form by generations of growers. The plant builds a tall, sturdy stalk lined with dozens of small cabbage-like buds, and those buds are the part you eat. It is a biennial grown as an annual, harvested in its first season well before it would set flowers.
This crop rewards patience. Brussels sprouts grow slowly and need a long run of cool weather to perform, so gardeners time them to mature in fall rather than under summer heat. Cold improves the eating quality, converting stored starch into sugar so the sprouts taste sweeter after the first light frosts.
They need steady care across a long season: rich soil, even moisture, and protection from the cabbage pests that locate every brassica in the garden. Get the timing right and feed them well, and a single stalk yields weeks of harvest worked 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, because that light fuels the strong stalk needed to carry a heavy crop. They tolerate a little partial sun, but genuine shade leaves you with weak plants and loose, disappointing sprouts.
Water
Keep the soil evenly moist through the long season, about 1 to 1.5 inches (2.5 to 4 cm) of water a week. Swinging between bone dry and saturated stresses the plant, so mulch to hold moisture in and keep the roots cool.
Soil
Plant in rich, well-drained loam full of organic matter, since these are hungry plants that occupy the bed for months. Aim for a pH between 6.0 and 7.0, leaning toward the higher end, which also helps hold clubroot in check by keeping the soil from turning acidic.
Temperature
Brussels sprouts are a cool-weather crop that grows best from about 41°F to 77°F (5°C to 25°C). Hardened plants shrug off frost and can stand in the garden until temperatures fall toward 20°F (-7°C), and that cold is precisely what sweetens the sprouts.
Humidity
Ordinary outdoor humidity suits them, so there is no number to chase. Airflow matters more than moisture in the air, because 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 begin side-dressing with nitrogen about 3 to 4 weeks after transplanting and continue through the growing season to keep the plant producing sprouts.
Pruning
Remove the lower leaves as they yellow and the sprouts beneath them mature, working steadily up the stalk. About 3 to 4 weeks before harvest, pinch out the growing tip to redirect energy into the remaining sprouts so they size up evenly.
Size & spacing
A mature plant reaches 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 large leaves and disease pressure stays low.
When to plant
Brussels sprouts are built for the second 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 to timing, feeding, or the steady pressure of cabbage-family pests. Catch the early signs on the leaves and roots and you can usually stop a problem before it travels up the stalk. Match what you see below, then act while the response still helps.
Daytime wilting and stunting traced to swollen roots
Clubroot is a soilborne pathogen of cole crops that builds up in acidic, waterlogged ground, and its first visible signs are wilting on warm days and poor growth. Lift a failing plant and the roots show the diagnostic swollen, club-shaped galls that disrupt water uptake, which is why the foliage flags in heat. No treatment cures an infected plant, so destroy affected plants roots and all, lime the bed toward pH 7.0 since the pathogen is suppressed in less acidic soil, and shift 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
Sprouts stay loose and leafy instead of tightening into firm buds
Blown, open sprouts are a temperature problem, not a soil one. Tight buds form when the plant sets sprouts in cool conditions; when those buds initiate in summer warmth, the scales separate and grow leafy rather than packing down, and any late shot of nitrogen drives still more loose foliage. The correction is twofold: schedule the crop so sprouts develop in cool fall weather, and top the plant 3 to 4 weeks before harvest to redirect energy into the buds already on the stalk.
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
Waxy gray aphids massed on leaf undersides and inside the buds
Cabbage aphids reproduce quickly on brassicas during warm spells and settle deep between the sprout leaves, where their waxy coating and sheltered position make contact sprays hard to land. The colonies read as dense, mealy gray patches on the leaf undersides, with curled foliage and sticky honeydew nearby. Dislodge them with a hard jet of water first, then coat the leaf undersides thoroughly with insecticidal soap or horticultural oil, since these work only on direct contact, and strip out any heavily colonized 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
Chewed, ragged leaves with green frass scattered below
Three caterpillars produce this damage, often on the same plant: the imported cabbageworm, the cabbage looper that arches its back as it crawls, and the small, restless diamondback moth larva. Turn the leaves to find the green caterpillars and their frass, and watch for the white butterflies whose eggs become cabbageworms. Handpicking thins the population, Bt or spinosad is most effective applied while the larvae are still small, and floating row cover excludes the egg-laying adults so the cycle never starts.
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 carries no toxins, and the worst a curious nibble produces is a bit of gas. Cook the sprouts before serving them to people, since the only real catch is a steady diet of large raw amounts.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe around cats. A cat that nibbles a leaf might end up slightly gassy, but no compound in the plant is harmful to it.
Dogs None
No real risk for dogs. One that gulps a large helping of raw sprouts may turn flatulent or get a passing upset stomach, and that is the extent of it.
Horses None
Non-toxic to horses. Brassica greens can produce gas in quantity, so offer them as an occasional treat rather than a regular feed.
Rabbits None
Suitable for rabbits in modest amounts. Add the leaves gradually, because a sudden volume of any cabbage-family green can upset their digestion.
Livestock None
Cattle, goats, and sheep can graze the foliage at normal levels without issue. Concern arises only with sustained, heavy raw feeding.
Birds None
Backyard hens readily peck the leaves and trimmings with no adverse effect.
People Safe
Grown as food and nutritious to eat. The sprouts are at their best cooked, and only a steady 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, ranging from old heirlooms to colorful modern hybrids. These are the ones worth knowing by name.
Long Island Improved
A long-standing open-pollinated heirloom on a fairly compact plant that served as the standard home-garden sprout for generations.
Jade Cross E
An early hybrid with good heat tolerance and heavy yields, which suits it to regions where the fall season is short.
Falstaff
A late cultivar bearing red-purple sprouts that hold 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 outside as transplants once they are sturdy enough to stand on 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 germinate readily. Sow about a quarter to half an inch (0.6 to 1.3 cm) deep in sterile starting mix 6 to 8 weeks ahead of your transplant date; emergence follows in 5 to 10 days and the seedlings reach planting size in 4 to 6 weeks. Harden them off before setting them out 18 to 24 inches (45 to 60 cm) apart, planting them to the same depth they held in their pots.
Myths
Brussels sprouts must be hit by a hard freeze before they are worth harvesting.
No freeze is required, and any firm sprout is ready to pick. Cool fall weather and light frosts do improve flavor by converting starch to sugar, which is the reason the crop is timed to mature in fall. Tight, well-formed sprouts can be harvested well before the first frost.
Cutting the top off a Brussels sprouts plant ruins the crop.
Topping is a recommended technique, not a blunder. Pinching out the growing tip 3 to 4 weeks before harvest halts upward growth and channels the plant's energy into the sprouts already set on the stalk so they fill out more evenly.