Vegetable · Brassicaceae
Broccoli
Brassica oleracea Italica Group
Plant it for cool weather and steady moisture, and broccoli hands you a main head and then weeks of tender side shoots.
Full sun
Every 3–5 days
32–77°F · 0–25°C
55–85 days
Overview
Broccoli is a cool-weather cousin of cabbage, and you grow it for that snug cluster of flower buds you cut before they ever open. It traces back to wild cabbage and shares a species with cauliflower, kale, and Brussels sprouts. Grown as an annual, it happily fits a spring crop, a fall crop, or both in the very same bed, so you have room to experiment.
Timing carries most of the weight here, and that is good news, because it means you can plan your way to success. Set plants out so the heads ripen while it is still cool, since heat coaxes the buds open into yellow flowers and brings the harvest to an early close. Get the season right and you will cut one firm central head, then keep gathering side shoots from the leaf axils for weeks after.
Broccoli asks for steady care, not anxious fussing, and that is exactly the kind a beginner can give. It is a heavy feeder that wants rich soil, even moisture, and full sun, and the handful of pests it draws are easy to manage with row cover. Cover those basics and you will find it is one of the most generous crops in the whole garden.
Care
The short version: give it full sun, rich soil full of compost, and even moisture of 1 to 1.5 inches of water a week. Aim for the heads to ripen in cool weather, feed it generously, and cut the head while the buds are still snug and tight.
Light
Broccoli is happiest in full sun, with at least 6 to 8 hours a day to build a firm, generous head. Where springs warm up in a hurry it will accept a little afternoon shade, and that gentle shade can even buy you some time before heat tempts it to bolt.
Water
Try to keep the soil evenly moist, somewhere around 1 to 1.5 inches of water a week. One deep weekly soaking serves it far better than little daily sprinkles, and that steady moisture matters most while the head is forming, since a dry stretch will stall its progress.
Soil
Settle it into rich, well drained loam that you have worked over with compost or well-rotted manure. A pH of 6.0 to 7.0 suits it nicely, and leaning toward the near-neutral end also helps keep clubroot at bay, since that trouble favors sour soil.
Temperature
Broccoli is a cool-season crop, most content from 32°F to 77°F (0°C to 25°C). It takes a light frost without complaint, but steady heat above about 80°F (27°C) can push the head to bolt before you get the chance to cut it.
Humidity
Plain outdoor humidity is all it needs, so there is no number to chase. Good airflow matters far more here, because crowded, damp foliage tends to invite the caterpillars and rots that bother brassicas.
Feeding
Broccoli is a hungry plant, a real heavy feeder. Work a balanced fertilizer into the bed before you plant, then side-dress with nitrogen about 3 to 4 weeks after transplanting to encourage strong leaves ahead of the head.
Pruning
There is no fussy pruning to learn here. Cut the central head with about 6 inches of stem while the buds are still tight, leave the plant right where it is for side shoots, and pluck off any lower leaves that yellow.
Repotting
Broccoli is no houseplant, so it never needs repotting. Just move seedlings out to the garden at 5 to 8 weeks old, before they grow rootbound, since cramped transplants have a habit of buttoning once they are set out.
Size & spacing
Plants grow 18 to 35 inches (45 to 90 cm) tall and roughly as wide. Give each one 18 to 24 inches (45 to 60 cm) of elbow room so air can move freely and every plant gets all the food it needs.
When to plant
Broccoli leans on the cool shoulders of the year, and that rhythm is easy to follow. Start seeds indoors in late winter for a spring crop or in July for a fall one, move the hardened-off transplants out while it is still cool, and gather the main head before summer heat or a hard frost arrives.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6-8 weeks before the last spring frost (early to mid-April in cold climates); sow again in early to late July for a fall crop
- Plant: Set hardened-off transplants out around 2-3 weeks before the last spring frost; transplant the fall crop in mid to late summer
- Harvest: Harvest the main head in late spring to early summer (spring crop) or in autumn (fall crop) when it is 3-6 inches across and buds are still tightly closed; side shoots follow for several weeks
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most broccoli hiccups turn up at the head or the roots, and they usually trace back to temperature or timing, so do not panic if something looks off. Spot the early signs and you can often still rescue this crop or the next planting. Find what matches your plant below, then act while it still does some good.
The head loosens and opens into yellow flowers
This is bolting, and heat is the usual cause once temperatures stay above about 80°F (27°C) as the head matures. A late harvest or a thirsty spell hurries it along as well. Cut the head the moment the buds begin to loosen, because quality slips fast, and try to time future crops so the heads fill out in cool weather.
Fix:
- Harvest immediately at the first sign of loosening buds; quality declines fast
- Cut bolted heads off so side shoots may still form in cooler weather
Plants wilt at midday and yellow despite enough water
The trouble is usually down at the roots, so pull a wilting plant and take a look. White legless maggots and tunneled roots point to cabbage root maggot, while swollen, knotted galls point to clubroot, a soil disease that loves acidic ground. Destroy any infected plants rather than composting them, shield the rest with row covers or stem collars, and give that bed a rest from brassicas for three to four years.
Fix:
- Remove and destroy infested or infected plants (do not compost clubroot material)
- For root maggot, protect remaining plants with row covers or collars at the stem base
- For clubroot, lime soil toward pH 7 and rotate out of brassicas for several years
A tiny head forms while the plant is still small
What you are seeing is buttoning, and it most often follows a cold spell that caught young transplants near or below 40°F (4°C). Oversized or rootbound seedlings and stress during settling in nudge a plant the same way. Go ahead and eat the little head, since it seldom sizes up, then replant with stocky transplants timed to the season and you will do better next round.
Fix:
- Harvest and eat the small head; the plant rarely sizes up afterward
- Keep remaining plants evenly watered and side-dress with nitrogen
- Replant with fresh, properly sized transplants timed to the season
Ragged holes in the leaves with green caterpillars
The likely visitor is the imported cabbageworm, the velvety green larva of the white cabbage butterfly, often with cabbage loopers and diamondback moth larvae along for the ride. Peek on the leaf undersides and down in the head for the caterpillars and their droppings. Handpick the ones you find, spray Bt or spinosad while the larvae are small, and tuck the plants under row cover from the day you transplant.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) or spinosad per label while larvae are small
- Soak harvested heads in cold salted water to drive out hidden caterpillars
Toxicity
You can relax completely, because broccoli is a food crop and gentle all around. No part of it is toxic to pets, livestock, or people, and the whole head and stem are good to eat. The one thing worth a glance is portion size, since a big helping of raw brassica can leave an animal a little gassy.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Broccoli is not poisonous to cats. Most simply walk past it, and the worst a curious nibble brings on is a touch of gas.
Dogs None
It is safe for dogs in small amounts, and plenty of them love a crunchy piece. Keep helpings modest, since a big serving of raw florets can leave a dog gassy or briefly off its dinner.
Horses Safe
There is nothing here that harms a horse. Brassicas can turn a bit gassy, so offer broccoli as an occasional snack rather than part of the regular feed.
Rabbits Safe
Rabbits can safely enjoy broccoli leaves and small pieces of the head. Bring it in slowly, because too much too soon may stir up some gas.
Livestock Safe
Cattle, goats, and sheep take broccoli and its trimmings in stride with no harm done. Only heavy, repeated feeding of raw brassicas is worth steering clear of.
Birds Safe
Chickens and other backyard birds peck happily at broccoli, leaves and florets alike. It makes a welcome green that costs you nothing once the heads are cut.
People Safe
Broccoli is a kitchen mainstay, lovely raw or cooked, with no part of the head or stem off limits. Just rinse garden-cut heads well to flush out any hidden caterpillars and soil.
No special handling precautions; wash garden-harvested heads to remove insects and soil before eating.
Varieties
There are dozens of broccoli varieties, sorted mostly into quick spring types and ones that hold up in heat. These are the names you are most likely to meet, and any of them is a kind place to start.
De Cicco
De Cicco is an early Italian heirloom that gives you a modest central head and then keeps offering side shoots over a nice long stretch.
Calabrese
Calabrese is the classic open-pollinated Italian type, with a medium green central head and a generous run of side shoots to follow.
Packman
Packman is an early hybrid that heads up in about 55 days from transplant, which makes it a comforting choice for a spring crop.
Green Magic
Green Magic is a heat-tolerant hybrid that keeps its quality once warm weather arrives, just where many others would give up and bolt.
Companions
Broccoli grows best beside plants that use space it leaves open or pull its pests away, and worst beside its own brassica cousins, which share the same diseases and crowd it for food.
Plant near
onions: Alliums make efficient use of space among widely spaced broccoli and their strong scent is traditionally credited with deterring some brassica pests
aromatic herbs (e.g., dill, chamomile): Flowering aromatic herbs attract beneficial insects, including parasitoid wasps that attack cabbageworm and other caterpillar pests
beets: Low-growing, light-feeding root crop that does not compete strongly with heavy-feeding broccoli for nitrogen or space
Keep apart
strawberries: Traditionally listed as a poor companion for cole crops; strawberries compete in the bed and are commonly recommended to be kept separate from brassicas
other heavy-feeding brassicas (cabbage, cauliflower, Brussels sprouts) in the same bed: Closely related crops share the same pests and soilborne diseases (clubroot, root maggot) and compete for nutrients; extensions recommend 3-4 year rotation away from all brassicas
How to propagate
Broccoli comes up from seed, started indoors and moved outside as a transplant for either a spring or a fall crop, which makes it a reassuring plant to raise from scratch.
SeedEasy
Sow indoors 6-8 weeks before the last spring frost, or sow indoors or direct in early to late July for a fall crop · Germinates in about 4-7 days in warm soil; reaches transplant size in 5-6 weeks (fall crop) to 6-8 weeks (spring crop)
Nearly everyone raises broccoli from seed, and it is a forgiving place to begin. Sow indoors 6 to 8 weeks before your last spring frost, or start a fall crop indoors or direct in July, and the seeds break ground in 4 to 7 days in warm soil. Harden the seedlings off gently, set them a touch deeper than they grew in the cell, and give them 18 to 24 inches (45 to 60 cm) apart. Pass over any leggy or rootbound transplant, since those are the ones that tend to button.
Myths
Once you cut the main head, the plant is finished and should be pulled.
Leave the plant in the ground after you take that central head and it carries right on. Smaller side shoots push out from the leaf axils, and you can harvest them for weeks, especially through cool fall weather. Pulling it early only cuts your reward short.
Frost ruins a broccoli crop.
Broccoli is a cool-season crop that takes a light frost in stride, so there is no need to worry. Fall plants keep growing and producing after the first frosts, and the cold often sweetens the heads. Only young transplants need a little protection once it dips below 32°F (0°C).