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Transplant broccoli out once seedlings have 4–6 true leaves — about 2–3 weeks before your last frost date — and it's ready to harvest 50–90 days after sowing.
The short answer
Ready in
50–90 days after planting out
Site
soil pH 6.8–7.5
Biggest risk
White blister
Core growing advice on this page is checked against named horticultural sources — see References.
Broccoli (Calabrese) (Brassica oleracea Italica Group)
12 sources cited · Verified
Quick Facts
Factor
Value
Soil pH
6.8 - 7.5
Optimal growing temp
15-24°C
Minimum survivable temp
-5°C
Time to harvest
50-90 days after planting out
Drainage
RHS: firm, fertile, well-drained soil in full sun.
Lifecycle
Annual.
Edible parts
flower heads, stems
Documented problems
6 diseases, 11 pests, 1 nutrient issue
At a Glance
Diseases
White blister
Albugo candida
RHS calabrese guide names white blister among named problems.
Damping-off (seedling collapse at soil line); Wilting with chlorotic, dropping leaves
Seed that rots before emergence, or seedlings collapsing at the soil line. A transplant-raising problem more than a bed problem: use fresh commercial mix, containers cleaned with a 10% bleach solution, and…
Alternaria leaf blight
medium
Alternaria dauci
Brown circular spots with concentric target rings, and small dark stem lesions on seedlings. Active between 60 and 90°F in moist conditions and overwinters on crop residue, so clearing the bed at season end plus a…
Downy mildew (general)
medium
Grey mould on the underside of the leaf with yellowing, later browning, on the upper surface directly above it. A moisture problem rather than a heat one: space widely so leaves dry, and water at soil level.
Black rot of brassicas
high
Xanthomonas campestris pv. campestris
Yellow V-shaped lesions cutting in from the leaf margin, with the point of the V aimed at a vein; the veins blacken and the rot can reach the stem. Seed- and transplant-borne, so it usually arrives on bought plants…
RHS calabrese guide names flea beetles on brassicas among named pests.
Mealy cabbage aphid
Brevicoryne brassicae
RHS calabrese guide names mealy cabbage aphid among named pests.
Cabbage root fly (US: cabbage maggot)
Delia radicum
RHS calabrese guide names cabbage root fly among named pests.
Harlequin bug
medium
Murgantia histrionica
A shield bug with a striking reddish-orange and black pattern; the eggs look like tiny black-and-white striped barrels laid in rows, which makes them easy to find and destroy. Piercing-sucking feeding leaves distinct…
Imported cabbageworm
medium
Pieris rapae
About an inch long and recognisable by its fuzzy appearance; Clemson rates it at about two-thirds the damage of a looper. It pupates in a chrysalis on the host plant, so it can be removed with the plant.
Cabbage looper
high
Trichoplusia ni
Up to 1.5 inches, moving in the distinctive looping gait, and it makes far bigger holes than diamondback moth -- Clemson puts one looper at roughly the damage of five diamondback larvae, so finding one matters more.…
Cabbage webworm
medium
Hellula rogatalis
Small, tan and brown striped with a dark head. It webs itself into the new growth for protection and attacks the buds and growing point, which causes lateral budding and can ruin a plant that would otherwise have made…
Cross-striped cabbageworm
medium
Evergestis rimosalis
Alternating black and white stripes across the back with a yellow stripe along the side, reaching about three-quarters of an inch. It hatches in masses and can rapidly skeletonise a plant, then drops to pupate just…
Diamondback moth caterpillar
high
Plutella xylostella
Clemson calls it "the most serious insect pest of brassica crops in South Carolina" despite being small, up to half an inch. The tell is a window-pane effect: the caterpillar eats the underside and leaves the upper…
Nutrient Issues
Boron (B)
deficiency
Correction
RHS names calabrese among the boron-sensitive vegetables, with hollow stem and browning heads as the symptoms. Boron is less available above pH 7, so avoid liming already-alkaline ground. Test soil pH rather than adding boron blind -- the margin between deficiency and toxicity is narrow.
Span reflects genuine variation between the cited authorities, not a single agreed figure.
Growth Stages
Stage
BBCH
Notes
Germination & seedling
0
Calabrese is raised from seed sown about 1–2cm deep, either in modules/pots or in situ where it is to grow — RHS notes calabrese resents root disturbance, so many gardeners sow direct or transplant while plants are still small. Seed germinates within about a week in warm soil (Clemson HGIC). Grow on to roughly 4–6 true leaves before planting out, and harden off module-raised plants first.
Vegetative growth (transplanting & leafing)
3
Plant or thin to about 30–45cm apart each way (RHS) — roughly 18in between plants (Clemson HGIC) — into firm, fertile, well-drained soil in full sun. Firm planting matters: loose soil gives poor, loose heads. Water in well, keep weed-free, feed with nitrogen for strong leafy growth, and net or fleece against pigeons and cabbage white caterpillars.
Head formation (curd/heading)
4
The central growing point forms a single domed head of tightly packed green flower buds. Steady, even moisture is critical now: RHS and Clemson HGIC both note that heat or water stress causes small heads, premature "buttoning", or bolting straight to flower. Keep plants consistently moist and mulch to hold soil moisture.
Harvest & side-shoots
8
Cut the main head while the buds are still tight and closed, before any yellow shows, when it is about 10–15cm across (RHS) — usually 50–90 days after sowing. Leave the plant in place: most calabrese varieties then produce smaller side-shoots from the leaf axils that crop for several more weeks.
When to pick: Cut the main head when 10-15cm across, well formed but still in bud, before flowers begin to open; side-shoots then produce further smaller heads for several weeks
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
Plasmodiophora brassicae produces resting spores that contaminate the soil and remain viable for many years, so any brassica following an infected crop is re-infected from the ground itself. Keep every brassica -- including radish, swede and turnip, which gardeners often forget are brassicas --…
These source is specific to this region. The full list of 12 sources behind this guide (Clemson Cooperative Extension, FAO EcoCrop, Royal Horticultural Society and others) is in the references of our UK guide to broccoli; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
How long does broccoli take to grow?
Typically 50–90 days after planting out, depending on cultivar and growing conditions.
What soil pH does broccoli need?
A pH of about 6.8–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.
What problems affect broccoli?
Our data links 6 diseases and 11 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
This page gives you the thresholds; the planner turns them into your own calendar. It works from what you can observe and measure in your garden rather than from dates written for somebody else’s latitude.
Every growing guide is checked against RHS, USDA Cooperative Extension, and other named horticultural authorities before publishing.
How this guide is put together
The growing data on this page — sowing windows, pests, diseases, soil and site requirements — comes from named horticultural sources, listed in References below, checked against international horticultural research and extension sources. An automated pipeline assembles that verified data into the page you're reading: it selects which facts to lead with and builds the surrounding prose and layout. It does not invent a date, a source or a number — where a verified value for a field isn't available, the page leaves it out rather than guessing. A person reviews and publishes each page; nothing goes live unverified.
Sketch your exact plot shape, pick your crops, and get a spacing-accurate bed layout with companion pairings and a rotation plan. Spacing, companion pairings and rotation are the same in every climate and both hemispheres — pair the layout it gives you with when to plant to set your own timing from soil temperature.
