A healthy brussel sprout plant looks like a small palm tree built out of cabbage: a thick, knee-high stalk studded top to bottom with dozens of tight green buttons. Get the timing and the feeding right and a single plant will hand you two to three pounds of sprouts, sweetened by the first hard frosts of fall. Get them wrong and you end up with a leafy stalk and a fistful of loose, bitter rosettes. The difference almost always comes down to a few decisions you make before and just after planting.
Brussels sprouts (Brassica oleracea) are slow-growing, long-season cole crops, cousins of cabbage, broccoli, kale, and cauliflower. They are not a fast crop or a forgiving one, but they are not difficult either once you understand what they are asking for: cool weather at the finish line, steady food and water along the way, and patience. Here is how to grow them from the moment you choose a planting date through the last harvest in the snow.
When to plant your brussel sprout plant
Brussels sprouts are a cool-season vegetable. They grow best between 60 and 70 degrees Fahrenheit and actually improve in cold weather, which is why in most of the country they perform best as a fall crop that matures as the nights turn frosty. Sprouts that size up during a hot spell tend to stay loose, leafy, and bitter, so the whole strategy is to schedule maturity for cool weather rather than warm.
The plant needs a long runway. Depending on the variety, expect roughly 80 to 110 days from setting a transplant in the ground to the first harvest, with 110 days a safe average to plan around. Work backward from your first fall frost date and aim to have transplants in the garden about 90 to 100 days before it. In most regions that means setting plants out in late spring to midsummer for a fall and early-winter harvest.
A spring crop is possible, but only in cooler climates or with an early, heat-tolerant variety planted as soon as the soil can be worked. The risk is real: in all but the most northern areas, summers are usually too warm for a spring planting to finish well, and the sprouts mature loose. If you garden where summers are hot, skip spring entirely and plant for fall.
Why transplants beat direct seeding
Direct sowing brussel sprouts in the garden is not recommended. The season is long, the young seedlings are easily lost, and you give up weeks of head start. Either grow your own transplants or buy stocky young plants from a nursery or farmers market.
To grow your own, sow seed indoors about 4 to 6 weeks before you plan to set plants out, covering the seed a quarter to a half inch deep. Some gardeners start even earlier, 8 to 10 weeks ahead, for a spring crop. Grow the seedlings under bright light so they stay compact rather than leggy, and harden them off outdoors for several days before transplanting. Begin in a shady, protected spot and gradually expose them to more sun.
Do not let transplants sit and get stunted or dried out in their cells before they go in the ground. A seedling that stalls in the pack never fully recovers its vigor, and vigor is exactly what carries this crop through its long season.
Sun, soil, and spacing your plants need
Give brussel sprouts full sun, at least six hours of direct light a day and more if you have it. They want fertile, moist, well-drained soil rich in organic matter, with a soil pH on the high side for vegetables, around 6.5 to 6.8. That slightly higher pH is not fussiness; it helps discourage clubroot, a soilborne disease of the cabbage family. The most reliable way to dial it in is a soil test, available through your regional Cooperative Extension office, which can also guide fertilizer and lime rates.
Before planting, work several inches of compost or aged manure into the bed. If you have not done a soil test, a general starting point is one to two pounds of a balanced fertilizer such as 10-10-10 per 100 square feet, mixed into the top four to six inches of soil.
Space plants generously. These get big, so set them 18 to 24 inches apart, with rows roughly 24 to 30 inches apart to leave room to walk and harvest. In beds, 24 inches in all directions works. Crowded plants compete for light and air and are more prone to disease.
One nutrient deserves special mention: boron. Brussels sprouts need more of it than most vegetables, and a shortage causes hollow stems and small, poorly formed buds. Only correct it if your plants show those symptoms, because too much boron is toxic. The traditional fix is to dissolve one level tablespoon of household borax in five quarts of water and sprinkle it evenly over 50 square feet of bed. Do not be tempted to use more.
Watering, feeding, and mulching through a long season
Cole crops have shallow roots and want steady moisture. Give the plants about 1 to 1.5 inches of water a week, counting rainfall, and do not let them dry out, especially during the heat of summer when the crop is sizing up its frame. Inconsistent water is one of the most common reasons sprouts stay small. Where possible, use soaker hoses or drip lines to keep water at the root zone and the foliage dry, which reduces disease.
Brussels sprouts are heavy feeders. Beyond the compost and starter fertilizer worked in at planting, side-dress with a nitrogen fertilizer about three to four weeks after transplanting, or when the plants reach roughly 12 inches tall, and repeat once or twice more through the season. Resist the urge to overfeed nitrogen late in the season, though: too much nitrogen pushes leafy growth and hollow stems at the expense of tight sprouts.
Lay down a 2 to 3 inch layer of mulch, such as straw, shredded leaves, or dry grass clippings, once the plants are established. Mulch keeps the soil cool and evenly moist and smothers the weeds that would otherwise steal water and nutrients. Cultivate only shallowly around the plants so you do not damage their roots.
Topping and removing leaves to size up the sprouts
Sprouts form in the leaf axils, the spots where each leaf meets the stalk, beginning at the base and working upward over several weeks. The plant naturally puts its earliest energy into growing tall, which is fine while it builds a frame but works against you once you want the buds to fill out.
Topping fixes that. When the lower sprouts reach about a half to three-quarters of an inch across, pinch out the growing tip at the top of the plant. Do this less than 60 days before your intended harvest, and no sooner than about three weeks before, depending on how uniform you want the crop. Removing the tip stops upward growth and redirects the plant’s energy into the developing buds, so the sprouts plump up and tend to mature all at once, which is handy if you want to harvest the whole stalk together.
Some gardeners also strip the lowest six to eight leaves as the sprouts below them firm up, removing a few more each week. This is optional in the home garden, and you should always leave several large, healthy leaves at the top to keep feeding the plant. Never strip a plant bare; the leaves are its engine.
Growing brussel sprouts in containers
You do not need a vegetable bed to grow a brussel sprout plant. They do well in large containers, which is useful on a patio or in a small garden, but they need real room for their roots. Give each plant a pot of at least 5 to 7 gallons, a minimum of 12 inches deep and 12 to 14 inches across; bump up to 15 gallons or 18 inches wide if you want two plants sharing a container.
Drainage matters more than almost anything else in a pot. Standing water rots the roots fast and is the single most common reason container sprouts fail, so make sure the pot has open drainage holes and use a quality potting mix rather than garden soil. Plastic pots hold moisture longer and need less frequent watering; unglazed clay breathes well and drains fast but dries out quickly, so you will water more often.
Because container soil dries faster than ground soil and the plants are still heavy feeders, stay on top of watering and feed regularly through the season. Otherwise, treat container plants exactly like those in the ground: full sun, steady moisture, and a cool finish in fall.
What to plant nearby, and what to keep away
Brussels sprouts share pests and diseases with their cabbage-family relatives, so it is smart to surround them with plants from other families to break up that vulnerability. Aromatic herbs and flowers earn their place here. Garlic and onions can mask the scent of the sprouts and are said to deter aphids and beetles. Marigolds discourage pests and release a compound that repels nematodes when tilled into the soil, and nasturtiums are credited with repelling squash bugs and whiteflies. Dill and basil attract beneficial insects such as ladybugs and parasitic wasps, and bush beans help by fixing nitrogen in the soil.
Mustard makes a useful trap crop: planted nearby, it draws the pests that would otherwise feed on your sprouts, and you simply pull and discard it once it is covered in insects.
A few plants make poor neighbors. Keep strawberries, kohlrabi, and pole beans away from brussel sprouts, and avoid crowding them in with their close cole-crop cousins, since broccoli, cauliflower, and cabbage attract the very same problems.
Pests and diseases that target the plant
The same insects that plague cabbage go after brussel sprouts. Cabbageworms, the green caterpillars that chew large, ragged holes in the leaves, are the usual headline pest; treat them at first sight with a product containing Bacillus thuringiensis (Bt), which is harmless to people but deadly to the caterpillars. Flea beetles riddle the foliage with tiny round shotholes, though minor damage rarely hurts the harvest. Aphids cluster in the developing sprouts and can often be knocked back with a forceful spray of water and the help of natural predators. Cutworms, cabbage loopers, diamondback moths, cabbage maggots, and harlequin bugs round out the cast.
Prevention beats spraying. Float a lightweight row cover over young plants to block egg-laying moths and beetles, set collars around stems to foil cutworms, and rotate cole crops so they grow in the same spot only once every three or four years to starve out soilborne larvae and disease. Above all, keep plants vigorous; a strong, well-watered plant shrugs off minor infestations that would cripple a weak one.
Diseases tend to be bacterial or fungal and thrive in wet, crowded conditions. Powdery and downy mildew, white mold, and various leaf spots are kept at bay by wide spacing, drip irrigation that keeps foliage dry, and good cleanup. Remove and destroy old plant debris at the end of the season, since spores overwinter in it. The high-pH, well-drained soil mentioned earlier is your main defense against clubroot.
Why your plant makes loose, leafy, or no sprouts
This is the problem that frustrates most growers, and nearly every cause traces back to the same handful of issues.
Loose, leafy sprouts that never firm into tight buttons almost always mean the heads developed in weather that was too warm. Above about 70 degrees, sprouts stay open and floppy. The cure is timing: plant so the sprouts mature in cool fall weather, use transplants rather than late spring seeding, and choose a faster-maturing variety if your cool window is short. Soil that was worked too loose just before planting can also produce loose sprouts, because the plant lacks a firm footing.
A plant that grows tall and leafy but sets few or no sprouts is usually getting too much nitrogen, not enough cool weather, or too little sun. Ease off late-season nitrogen, make sure the plant gets its full six-plus hours of sun, and be patient, since many varieties need a solid 80 to 100 days before buttons appear at all. Topping the plant, as described above, also helps push energy into bud formation.
Bitter sprouts come from heat as well, or from leaving mature sprouts on the plant too long. Harvest on time and let frost, not the calendar, sweeten them. Bolting, where a young plant throws up a flower stalk and never forms heads, is triggered by a long stretch of temperatures below 50 degrees while the plant is still small; protect early transplants from prolonged cold and choose bolt-resistant varieties. Hollow stems point to either a boron deficiency or excessive nitrogen driving too-fast growth, so check your feeding and correct boron only if symptoms appear.
Harvesting after frost for the sweetest sprouts
Sprouts mature from the bottom of the stalk upward, so the lowest buds are ready first. Start picking when they are firm, green, and about 1 to 1.5 inches across, like tiny cabbages; pick or twist them off and remove any yellowing lower leaves as you go, but leave the upper leaves to keep the plant producing. If you topped the plant, the stalk will fill out more evenly and you can often cut the whole thing at once.
This is the payoff for a long season: a light frost or two improves the flavor dramatically. As temperatures drop, the plant converts starches to sugars as a natural antifreeze, turning the sprouts mild and sweet instead of sulfury. The plants are hardy down to around 20 degrees, so in many regions you can keep harvesting well into late fall and even early winter, pulling sprouts as you need them. In cold climates, gardeners sometimes pull the whole stalk after a hard frost or bury plants up to their tops in hay and harvest through the winter. Once you pick a sprout, no new one grows in its place, so work your way up the stalk.
A healthy plant yields roughly 2 to 3 pounds of sprouts, and a 10-foot row commonly gives 7 to 10 pounds. Fresh sprouts taste best, but you can store unwashed sprouts in a perforated plastic bag in the refrigerator for a few weeks. And do not toss the leafy tops; cook them like collards.
Brussels sprouts ask for more patience than almost anything else in the vegetable garden, holding their ground from spring through the first snows. Plant them for a cool finish, feed and water them steadily, top them at the right moment, and the reward is a stalk of sweet, frost-kissed buttons at exactly the time of year when the rest of the garden has given up. Pick your variety, mark your fall frost date, and count backward.