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Grow broccoli as a cool-season crop, timing it so the heads mature at 65 to 75°F — start seeds indoors 6 to 8 weeks before transplanting, set plants out 18 inches apart in rich soil and full sun, keep them consistently watered and fed, and cut the central head while the buds are still tight and green. The single biggest factor in success is temperature: broccoli that matures in summer heat bolts into loose yellow flowers, so most gardeners grow it as a spring crop that finishes before heat, or a fall crop that matures as the weather cools.
Broccoli rewards good timing and generous feeding, and unlike many vegetables it keeps giving after the first harvest through side shoots. Here is the full sequence, with the numbers that decide whether you get tight green heads or a bolted mess.
The Temperature Window That Controls Growing Broccoli
Broccoli grows best when daytime temperatures sit between 65 and 75°F, and it is this window — not a date — that you are aiming the crop at. Above the mid-70s°F for a sustained period, plants bolt; below freezing for long stretches, growth stops. Because a spring crop races against rising summer heat, many gardeners find the fall crop easier and higher quality: it matures into steadily cooling weather, and a light frost actually sweetens the heads.
- Spring crop: start seeds indoors 6 to 8 weeks before your last frost; transplant 2 to 3 weeks before the last frost so heads mature before summer heat.
- Fall crop: count back the variety's days-to-maturity plus about two weeks from your first fall frost, then start seeds so transplants go out in mid to late summer.
Starting seeds and transplanting
Broccoli transplants well, which makes indoor starting the reliable route, especially for spring crops that need a head start before heat.
- Sow seeds 1/4 to 1/2 inch deep in cells or trays, 6 to 8 weeks before transplant date. Keep soil at 65 to 75°F for fast germination — seeds sprout in 5 to 10 days.
- Give strong light. Seedlings stretch and flop under weak light; a bright window is rarely enough. See do you need grow lights to start seeds.
- Harden off for 7 to 10 days before transplanting, gradually exposing seedlings to outdoor conditions — the full method is in how to harden off seedlings.
- Transplant at the 4 to 6 true-leaf stage, setting plants slightly deeper than they grew and spacing them 18 inches apart.
In mild-summer regions you can also direct-sow broccoli, thinning seedlings to 18 inches, but transplants give more predictable timing.
Broccoli Soil, Sun and Spacing
Broccoli is a heavy feeder in the cabbage family and wants full sun (6+ hours), rich soil high in organic matter, and a near-neutral pH of 6.0 to 7.0. That slightly higher pH also helps suppress clubroot, a serious brassica soil disease. Work 2 to 3 inches of compost into the bed before planting.
| Spacing | Between plants | Between rows | Result |
|---|---|---|---|
| Standard | 18 in | 24 to 36 in | Largest central heads |
| Intensive | 12 to 15 in | 18 to 24 in | Smaller heads, more side shoots per area |
Feeding and watering
Consistent moisture and steady nitrogen early on drive the leafy growth that supports a big head. Give broccoli about 1 to 1.5 inches of water a week, keeping the soil evenly moist — irregular watering stresses plants and encourages bolting and hollow stems.
Feed at transplant with a balanced fertilizer, then side-dress with nitrogen about three weeks later when plants are establishing, and again after you cut the main head to fuel side shoots. Avoid overdoing nitrogen right as heads form, which can cause hollow stem. A general vegetable feed works well; the ranked options are in best vegetable garden fertilizer, chosen by the method in how we rank.
Why heads button or bolt, and how to prevent it
Two disappointing outcomes have the same root cause — stress — but different triggers:
- Buttoning: tiny premature heads on small plants. Caused by transplant shock, root-bound seedlings, or a cold snap that checked young plants. Prevention: transplant on time, never let seedlings get root-bound, and harden off properly.
- Bolting: the head opens into yellow flowers. Caused by heat and drought. Prevention: time the crop for cool maturity, water consistently, and harvest promptly.
Once you see yellow showing between the buds, cut immediately — the window from tight head to open flower can be as short as a day or two in warm weather.
Pests and diseases to watch
| Problem | Sign | Control |
|---|---|---|
| Cabbage worms/loopers | Green caterpillars, chewed leaves, frass in heads | Row cover, hand-pick, Bt spray (Bacillus thuringiensis) |
| Aphids | Clusters on new growth and in heads | Strong water spray, insecticidal soap |
| Cabbage root maggot | Wilting, stunted plants; larvae at roots | Collars at soil line, floating row cover at transplant |
| Clubroot | Swollen, distorted roots; wilting | Raise pH toward 7.0; rotate brassicas; buy clean stock |
| Downy mildew | Yellow patches, gray fuzz underneath leaves | Improve air flow, water at the base, space adequately |
A floating row cover installed at transplant is the single most effective defense, blocking the moths and flies that cause most brassica damage.
Harvesting Broccoli: The Main Head and Side Shoots
Harvest when the central head is full-sized for the variety, firm, and the buds are still tightly closed and deep green. Cut the stem 5 to 6 inches below the head at a slant so water sheds off the cut. Do this in the cool of the morning.
After the main cut, leave the plant in the ground and keep it watered and fed. Most varieties then push side shoots — small broccoli heads from the leaf axils — that you can harvest every few days for three to five weeks. Cut them young, before they flower, and the plant keeps producing. Sprouting broccoli types are bred for this extended side-shoot harvest and skip the big central head entirely.
Storing and getting the most from the harvest
Broccoli is at its best within a day or two of cutting, when the sugars are highest and the texture crisp. Store unwashed heads loosely wrapped in the refrigerator crisper, where they hold for about a week; wash only just before use, since surface moisture speeds spoilage. For longer storage, broccoli freezes well after a short blanch — plunge florets into boiling water for three minutes, cool immediately in ice water, drain and freeze, and they keep their color and texture for months.
Do not waste the plant beyond the head. The leaves are edible and cook like collards, the tender upper stalks are sweet once peeled, and the side shoots that follow the main head extend the eating for weeks. Harvesting in the cool of the morning and chilling the heads promptly makes a noticeable difference to how long they keep and how sweet they taste, because warmth converts the sugars to starch quickly after cutting.
Next steps and related crops
Broccoli sits alongside the other cool-season brassicas, and their timing overlaps. If you are planning a fall garden, pair it with the crops in fall vegetables to plant, and use the succession planting schedule to keep heads coming. For pinning down the exact planting dates, see when to plant broccoli, and for a closely related cool-season brassica, when to plant kale. Everything else is at the seeds and vegetable growing hub.