Vegetable · Brassicaceae
Broccoli
Brassica oleracea Italica Group
Give it cool weather and steady moisture, and broccoli hands over a main head plus weeks of side shoots.
Full sun
Every 3–5 days
32–77°F · 0–25°C
55–85 days
Overview
Broccoli is a cool-weather member of the cabbage family, and you're growing it for that tight cluster of flower buds you snip before they open. It came from wild cabbage and shares a species with cauliflower, kale, and Brussels sprouts. You grow it as an annual, and it's happy as a spring crop, a fall crop, or both in the same bed.
Want to know the real secret? It's timing. Set plants out so the heads mature while it's still cool, because heat pops the buds open into yellow flowers and that's the end of the harvest. Get the season right, though, and you'll cut one firm central head and then keep grabbing side shoots from the leaf axils for weeks.
Broccoli doesn't need fussing, just steadiness. It's a heavy feeder that likes rich soil, even moisture, and full sun, and the pests it draws are easy enough to keep out with row cover. Cover those basics and you've got one of the most productive plants in the whole garden.
Care
The short version: full sun, rich soil with lots of compost, and even moisture of 1 to 1.5 inches of water a week. Time the crop so the heads mature when it's cool, feed it well, and cut the head while the buds are still tight.
Light
Broccoli really wants full sun, at least 6 to 8 hours a day, to put together a firm head. Where springs heat up quick it'll take a bit of afternoon shade, and honestly that shade can buy you some time before the heat makes it bolt.
Water
Keep the soil evenly moist, somewhere around 1 to 1.5 inches of water a week. One good deep soak each week beats a bunch of light sprinkles, and that even moisture matters most while the head's forming, since a dry patch will stall it.
Soil
Get it into rich, well drained loam that you've mixed with compost or well-rotted manure. A pH of 6.0 to 7.0 works great, and leaning near neutral also helps hold off clubroot, which loves sour soil.
Temperature
Broccoli is a cool-season crop and happiest from 32°F to 77°F (0°C to 25°C). A light frost? No problem. But steady heat above about 80°F (27°C) makes the head bolt before you ever get to cut it.
Humidity
Regular outdoor humidity is fine, so there's no number to chase. What matters way more is airflow, because crowded, damp leaves are exactly what the caterpillars and rots that bug brassicas are looking for.
Feeding
Broccoli eats a lot, so think of it as a heavy feeder. Mix a balanced fertilizer into the bed before planting, then side-dress with nitrogen about 3 to 4 weeks after transplanting to push strong leaves ahead of the head.
Pruning
There's no real pruning here. Just cut the central head with about 6 inches of stem while the buds are still tight, leave the plant where it is for side shoots, and pull off any lower leaves that go yellow.
Repotting
Broccoli isn't a houseplant, so you'll never repot it. Move seedlings to the garden at 5 to 8 weeks old, before they get rootbound, because cramped transplants have a way of buttoning once they're set out.
Size & spacing
Plants get 18 to 35 inches (45 to 90 cm) tall and about as wide. Give each one 18 to 24 inches (45 to 60 cm) of space so air moves around and every plant has enough to eat.
When to plant
Broccoli likes the cool ends of the year, plain and simple. 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's still cool, and pick the main head before summer heat or a hard frost rolls in.
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 trouble pops up at the head or the roots, and it usually comes down to temperature or timing. The good news? Catch it early and you can often still save this crop or the next one. Find what matches your plant below, then act while it'll actually help.
That tight head goes loose and bursts into yellow blooms
That's bolting, and heat is usually behind it once temperatures stay above about 80°F (27°C) while the head matures. A late harvest or a dry spell speeds it up too. Cut the head the second the buds start to loosen, because quality drops fast, and try to time future crops so the heads fill out when it's cool.
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
Droopy, yellowing plants even though the watering's fine
Usually the trouble's down at the roots, so pull a wilting plant and have a look. White legless maggots and tunneled roots? That's cabbage root maggot. Swollen, knotted galls? That's clubroot, a soil disease that loves acidic ground. Toss infected plants instead of composting them, protect the rest with row covers or stem collars, and keep brassicas out of that bed 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 little button of a head shows up far too early
That's buttoning, and it usually goes back to a cold spell that caught young transplants near or below 40°F (4°C). Oversized or rootbound seedlings and stress while settling in do the same thing. Just eat the little head, since it almost never sizes up, then replant with stocky transplants timed to the season.
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
Leaves riddled with chewed holes and little green caterpillars
Odds are it's the imported cabbageworm, the velvety green larva of the white cabbage butterfly, and often cabbage loopers and diamondback moth larvae are in on it too. Check the leaf undersides and down in the head for the caterpillars and their droppings. Handpick what 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
No need to stress here, since broccoli is a food crop and totally safe. No part of it is toxic to pets, livestock, or people, and the whole head and stem are good eating. The only thing to keep an eye on is how much, because a big pile of raw brassica can leave an animal kind of gassy.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Broccoli isn't poisonous to cats. Most cats just walk on by, and the worst a curious nibble does is bring on a little gas.
Dogs None
It's safe for dogs in small amounts, and lots of them love a crunchy piece. Keep servings small, though, because a big helping of raw florets can leave a dog gassy or off its food for a bit.
Horses Safe
There's nothing toxic in it for a horse. Brassicas can be a little gassy, so treat broccoli as an occasional snack instead of a regular feed.
Rabbits Safe
Rabbits can eat broccoli leaves and small bits of the head just fine. Bring it in slowly, because too much too fast can stir up some gas.
Livestock Safe
Cattle, goats, and sheep handle broccoli and its trimmings without any harm. The only thing to skip is heavy, repeated feeding of raw brassicas.
Birds Safe
Chickens and other backyard birds peck at broccoli no problem, leaves and florets alike. It's a welcome green that costs you nothing once the heads are cut.
People Safe
Broccoli is a kitchen staple, great raw or cooked, with no part of the head or stem off limits. Just wash garden-cut heads well to clear 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, mostly split between quick spring types and ones that handle heat. Here are the names you'll bump into most often.
De Cicco
De Cicco is an early Italian heirloom that gives you a modest central head and then just keeps throwing side shoots over a long stretch.
Calabrese
Calabrese is the classic open-pollinated Italian type, with a medium green central head and a generous run of side shoots after.
Packman
Packman is an early hybrid that heads up in about 55 days from transplant, which is why folks love it for spring crops.
Green Magic
Green Magic is a heat-tolerant hybrid that keeps its quality once warm weather hits, right where a lot of others would just 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
You grow broccoli from seed, starting it indoors and moving it out as a transplant for either a spring or a fall crop.
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)
Pretty much everyone grows broccoli from seed. Sow it indoors 6 to 8 weeks before your last spring frost, or start a fall crop indoors or direct in July, and the seeds come up in 4 to 7 days in warm soil. Harden the seedlings off, set them a bit deeper than they grew in the cell, and space them 18 to 24 inches (45 to 60 cm) apart. Skip any leggy or rootbound transplant, since those are the ones that button.
Myths
Cut off that big head and that's it, the plant's finished, so yank it out.
Leave the plant in the ground after you take that central head and it just keeps going. Smaller side shoots push out from the leaf axils, so you can harvest them for weeks, especially through cool fall weather. Why pull it and lose all that?
Frost ruins a broccoli crop.
Broccoli's a cool-season crop, so a light frost? It takes it in stride. Fall plants keep growing and producing after the first frosts, and the cold often makes the heads sweeter. Only young transplants need a little cover once it drops below 32°F (0°C).