Vegetable · Brassicaceae
Broccoli
Brassica oleracea Italica Group
Built for cool weather and steady moisture, broccoli forms one firm head and then 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, grown for the dense, blue-green dome of flower buds that crowns a thick central stalk. Those buds stay tightly closed and pebbled until you cut them, and the plant descends from wild cabbage, sharing a species with cauliflower, kale, and Brussels sprouts. Grown as an annual, it fits a spring crop, a fall crop, or both in one bed.
Watch the head and you read the whole plant. Cut while the buds form a firm, fine-grained cluster, because heat swells and parts them, opening little yellow flowers that scatter across the surface and end the harvest. Take that central head in time and the broad, waxy leaves keep working, pushing side shoots with their own small green heads from the leaf axils for weeks.
Up close, broccoli is a sturdy, leafy plant. It is a heavy feeder behind those large gray-green leaves and the heavy central stem, and it wants rich soil, even moisture, and full sun. A few familiar caterpillars chew the foliage, but row cover keeps them clear, and the plant stays one of the most productive in the garden.
Care
The short version: full sun, rich soil thick with compost, and even moisture of 1 to 1.5 inches of water a week. Bring the firm bud head to maturity in cool weather, feed the plant well, and cut the head while every bud is still closed and tight.
Light
Broccoli needs full sun, at least 6 to 8 hours a day, to pack the buds into a firm, tight head. Where springs warm fast it takes a little afternoon shade across its broad leaves, and that shade holds the head closed a while longer before heat forces it open.
Water
Keep the soil evenly moist, around 1 to 1.5 inches of water a week, so the buds swell into a dense head rather than a loose one. A single deep weekly soaking beats light sprinklings, and that moisture counts most while the head is forming, since a dry spell leaves the cluster small and uneven.
Soil
Set it in rich, well drained loam worked through with compost or well-rotted manure, the kind of ground that builds a heavy stalk and a full head. A pH of 6.0 to 7.0 suits it, and the near-neutral end holds back clubroot, which knots the roots in sour soil.
Temperature
Broccoli is a cool-season crop, at its firmest from 32°F to 77°F (0°C to 25°C). The blue-green head takes a light frost, but sustained heat above about 80°F (27°C) loosens and parts the buds before you can cut them.
Humidity
Ordinary outdoor humidity is fine, so there is no figure to hit. Airflow around the leaves matters more, since crowded, damp foliage draws the caterpillars and rots that chew and spot brassicas.
Feeding
Behind the head, broccoli is a heavy feeder. Work a balanced fertilizer into the bed before planting, then side-dress with nitrogen about 3 to 4 weeks after transplanting to drive the large, waxy leaves that fuel a full head.
Pruning
There is no real pruning to do. Cut the central head with about 6 inches of thick stem while every bud is still closed and tight, leave the plant for the smaller side shoots, and strip off any lower leaves that yellow.
Repotting
Broccoli is not a houseplant, so it is never repotted. Move the stocky seedlings to the garden at 5 to 8 weeks old, before the roots coil and bind, since cramped transplants throw a tiny premature head once set out.
Size & spacing
A mature plant stands 18 to 35 inches (45 to 90 cm) tall on a stout stem and spreads about as wide with its leaves. Give each one 18 to 24 inches (45 to 60 cm) so the broad foliage has room and air moves between plants.
When to plant
Broccoli forms its best heads at the cool ends of the year. Start seeds indoors in late winter for a spring crop or in July for a fall one, set the hardened-off transplants out while it stays cool, and cut the firm central head before summer heat or a hard frost spoils the buds.
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 shows on the head or below at the roots, and it usually comes down to temperature or timing. Read the buds and the leaves early and you can still save this crop or the next planting. Match what you see below, then act while it helps.
Tight green buds swell apart and flash yellow petals
When the tight green buds swell, separate, and open into loose yellow flowers, the plant is bolting, driven by heat once temperatures hold above about 80°F (27°C) as the head matures. A late harvest or water stress pushes it faster. Cut the head the moment the buds start to loosen, since quality drops fast, and time future crops so the heads firm up 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
Limp, sun-flattened leaves turning yellow over moist soil
When the leaves wilt at midday and yellow with plenty of water, the roots are the place to look. White legless maggots and tunneled roots mean cabbage root maggot, while swollen, knotted galls mean clubroot, a soil disease that thrives in acidic ground. Destroy infected plants rather than composting them, ring 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 tiny bud cluster crowns an undersized plant
A small plant that throws a head only an inch or two across is showing buttoning, usually after a cold spell that hit young transplants near or below 40°F (4°C). Oversized or rootbound seedlings and a hard start do the same. That little head rarely fills out, so cut and eat it, 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
Jagged chewed openings across leaves patrolled by velvety caterpillars
The velvety green larva chewing ragged holes is the imported cabbageworm, offspring of the white cabbage butterfly, often alongside cabbage loopers and diamondback moth larvae. Look on the leaf undersides and down between the buds for the caterpillars and their dark frass pellets. Handpick what you find, spray Bt or spinosad while the larvae are small, and drape row cover over the plants 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
Broccoli is a food crop and safe all around. No part of it is toxic to pets, livestock, or people, and the entire head and the thick stem are good to eat. The only thing worth watching is portion size, since a large helping of raw brassica can leave an animal gassy.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Broccoli is not poisonous to cats. Most cats sniff the leaves and walk off, and the worst a curious nibble brings is a little gas.
Dogs None
It is safe for dogs in small amounts, and many crunch a raw floret happily. Keep servings modest, since a big helping of the raw buds and stem can leave a dog gassy or briefly off its food.
Horses Safe
There is nothing toxic here for a horse. The leaves and stems can run a bit gassy, so offer broccoli as an occasional snack rather than a regular feed.
Rabbits Safe
Rabbits can eat the broccoli leaves and small bits of the bud head safely. Introduce it slowly, since too much too fast may bring on gas.
Livestock Safe
Cattle, goats, and sheep handle broccoli leaves, stems, and trimmings without harm. Only heavy, repeated feeding of the raw plant is worth avoiding.
Birds Safe
Chickens and other backyard birds peck at broccoli with no trouble, the leaves and the green florets alike. It is a welcome green that costs nothing once the heads are cut.
People Safe
Broccoli is a kitchen staple, good raw or cooked, with no part of the head or the thick stem off limits. Just wash garden-cut heads well to clear any caterpillars tucked among the buds and soil.
No special handling precautions; wash garden-harvested heads to remove insects and soil before eating.
Varieties
Dozens of broccoli varieties exist, split mostly between quick spring types and heat-tolerant ones, and they differ in head size, color, and how freely they branch. These are the names you will meet most.
De Cicco
De Cicco is an early Italian heirloom with a modest central head and a long run of small side shoots that follow.
Calabrese
Calabrese is the classic open-pollinated Italian type, marked by a medium green central head and a generous flush of side shoots after.
Packman
Packman is an early hybrid whose head fills out in about 55 days from transplant, which suits a quick spring crop.
Green Magic
Green Magic is a heat-tolerant hybrid that keeps its tight, even head once warm weather arrives, where many others loosen 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 grows from seed, started indoors and moved out as a sturdy little 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)
Almost all broccoli starts as seed, small round seeds that sprout fast. Sow indoors 6 to 8 weeks before your last spring frost, or start a fall crop indoors or direct in July, and the seedlings break the surface in 4 to 7 days in warm soil. Harden them off, set each a little deeper than it grew in the cell so the stem stands firm, and space them 18 to 24 inches (45 to 60 cm) apart. Pass over any leggy or rootbound transplant, since those throw a premature button.
Myths
Take the big central crown and the plant is spent; nothing more worth cutting will follow.
Once the central head is gone, the leafy plant is far from finished. Smaller side shoots, each a little green head of its own, push from the leaf axils, and you can harvest them for weeks, especially through cool fall weather. Pull the plant early and you lose all those second heads.
Frost ruins a broccoli crop.
The blue-green broccoli plant is a cool-season grower that takes a light frost in stride. Fall plants keep growing and producing after the first frosts, and the cold often sweetens the heads. Only young transplants need cover once it drops below 32°F (0°C).