Vegetable · Brassicaceae
Brussels Sprouts
Brassica oleracea Gemmifera Group
Plant for fall, let a light frost work on the stalk, and the little buds come in firm, tight, and sweet.
Full sun
Every 3–7 days
41–77°F · 5–25°C
80–110 days
Overview
Brussels sprouts are a cool-season cabbage relative, the same species as broccoli, kale, and cauliflower, each one bred into a different shape over generations. This plant throws up a tall, sturdy stalk and studs it with dozens of little cabbage-like buds spiraling all the way up, and those tight green knobs are the sprouts you eat. It is a biennial grown as an annual, harvested in its first season long before it would ever bolt and flower.
This crop rewards patience. The stalk thickens slowly and needs a long run of cool weather to set good buds, so gardeners time it to fill out in fall instead of summer heat. Cold actually improves the sprouts, turning their starch to sugar so each firm bud tastes sweeter after the first light frosts touch the plant.
They ask for steady care across a long season: rich soil under the roots, even moisture, and a guard against the cabbage pests that hunt down every brassica leaf in the garden. Time it right and feed the stalk well, and a single plant hands you weeks of sprouts picked from the bottom up.
Care
The short version: full sun and rich, evenly moist soil, planted so the buds set and tighten in cool fall weather, with steady feeding across a long season and a sharp eye on the leaves for cabbage pests.
Light
Brussels sprouts want full sun, ideally 6 or more hours a day, to drive the thick stalk that holds a heavy load of sprouts. They take a little partial sun, but real shade leaves you with a thin, weak stalk and loose, disappointing buds.
Water
Keep the soil evenly moist the whole long season, around 1 to 1.5 inches (2.5 to 4 cm) of water a week. Swinging from bone dry to soaking stresses the plant and the buds, so mulch over the roots to hold moisture and keep them cool.
Soil
Plant in rich, well-drained loam loaded with organic matter, since the stalk feeds heavily and stands in the ground for months. Aim for a pH between 6.0 and 7.0, leaning toward the higher end, which also helps hold clubroot off the roots.
Temperature
Brussels sprouts are a cool-weather crop that runs best from about 41°F to 77°F (5°C to 25°C). A hardened stalk shrugs off frost and stands in the garden until temperatures fall toward 20°F (-7°C), and that cold is exactly what sweetens the buds.
Humidity
Ordinary outdoor humidity suits them, so there is no number to chase. Good airflow matters more than moisture in the air, because crowded, damp leaves invite 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 on through the season to keep the stalk pushing out fresh buds.
Pruning
Strip the lower leaves as they yellow and the buds beneath them firm up, working steadily up the stalk. About 3 to 4 weeks before you want to harvest, pinch out the growing tip to drive energy into the sprouts already set so they swell evenly.
Size & spacing
A mature stalk stands 2 to 4 feet (60 to 120 cm) tall and spreads about as wide with its big leaves. Set transplants 18 to 24 inches (45 to 60 cm) apart so air moves between those broad leaves and disease stays down.
When to plant
Brussels sprouts are built for the back half of the year. Start the seed in late spring, set the young plants out in early to midsummer, and harvest from early fall into winter, twisting the firm buds off the bottom of the stalk first and working up 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 first signs on the broad leaves and down at the roots and you can usually stop a problem before it climbs the stalk. Match what you see below, then act while it still helps.
Wilting tops over swollen, distorted roots
Clubroot is a soilborne disease that takes hold in acidic, soggy ground and shows first in the top of the plant, which flags and wilts on warm days while the stalk stays short and stunted. Pull a struggling plant and the cause is plain in the roots: swollen, club-shaped galls in place of slender feeder roots. Nothing reverses it once it sets in, so lift the infected plants roots and all and destroy them, lime the bed toward pH 7.0, and shift the 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
Buds that stay loose and leafy instead of balling up tight
Blown, open sprouts show that the little buds packed on warmth rather than cold. Instead of curling into firm round knobs, they spread into loose, leafy rosettes along the stalk, and a late shot of nitrogen pushes that loose growth even further. Shift the planting so the buds form in the chill of fall, and pinch off the top 3 to 4 weeks before harvest to help the remaining sprouts draw in tight.
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
A powdery gray crust tucked into the sprouts
Cabbage aphids coat the plant as a dusty, gray-green mass with a waxy bloom, packing themselves down between the tight bud leaves where fingers and sprays can barely reach. Turn a leaf over and you find the colonies clinging to the underside, the foliage curling around them, and a sticky film of honeydew on the surface. Knock them loose with a hard jet of water, then coat the leaf undersides with insecticidal soap or horticultural oil and strip away any lower leaves crusted over with them.
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 droppings caught in the folds
Three green caterpillars chew these ragged holes, and they blend right into the broad leaves: the velvety imported cabbageworm, the cabbage looper that humps its back as it crawls, and the small, whip-thin diamondback larva that wriggles when touched. Lift the leaves and look for the caterpillars and their dark green frass, and watch for the white butterflies drifting over the plant. Pick off what you find, spray Bt or spinosad while they are still tiny, and drape the plants in floating row cover to keep the moths from laying.
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. Nothing in the leaves, stalk, or buds is toxic, and the worst a curious nibble brings is a bit of gas. Cook the sprouts before serving them 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 around cats. A nibble off one of the broad leaves might leave a cat a little gassy, but nothing in the stalk, leaves, or buds will do it harm.
Dogs None
Nothing to worry about. A dog that gulps a big pile of the raw sprouts might turn flatulent or have a briefly upset stomach, and that is as bad as it gets.
Horses None
Not toxic to horses. The leafy brassica greens can turn a horse gassy in any quantity, so let them be an occasional nibble rather than a regular feed.
Rabbits None
Fine for rabbits in small amounts. Bring the leaves in slowly, since a sudden load of any cabbage-family green can loosen their digestion.
Livestock None
Cattle, goats, and sheep can graze the leaves and stalks without trouble at normal levels. Only steady, heavy raw feeding raises any concern.
Birds None
Backyard hens peck happily at the leaves and trimmings with no ill effect.
People Safe
Grown to be eaten and good for you. The buds 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 green heirlooms to colorful modern hybrids. These are the ones worth knowing by name.
Long Island Improved
An open-pollinated heirloom on a shorter, compact stalk, the home-garden standard that grew dependable green sprouts for generations.
Jade Cross E
An early hybrid that takes heat and packs the stalk with a heavy set of sprouts, a sound choice where the fall season runs short.
Falstaff
A late variety whose sprouts come in a deep red-purple that holds much of its color even 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 grow from seed, started indoors and carried out as transplants once the seedlings are 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
The small round seeds sprout readily. Press them about a quarter to half an inch (0.6 to 1.3 cm) into sterile starting mix 6 to 8 weeks before transplant day, and the seedlings push their first leaves through in 5 to 10 days and stand up to planting size in 4 to 6 weeks. Harden them off, then set the young plants 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.
No freeze is required, and any firm, tight bud on the stalk is ready to twist off. What cool fall weather and light frosts do is sweeten the flavor by turning starch to sugar, which is the reason the crop is timed for fall. You can pick fine, solid sprouts well before the first frost.
Cutting the top off a Brussels sprouts plant ruins the crop.
Topping is a deliberate trick, not damage. Pinching out the growing tip 3 to 4 weeks before harvest stops the stalk pushing taller and sends that energy down into the buds already set, so they swell and fill out more evenly.