The short version: Broccoli, cabbage, cauliflower and kale sown in January and February have time to build a big frame of leaves before cold, short days slow them. Brussels sprouts need longer, so most gardens sow them by December or January. Raise seedlings in cell trays under 30 to 50% shade cloth, sow in the evening, keep the mix damp and mesh them from the start. The tropics wait for the dry season, and arid gardens for cooler nights.
Sowing cauliflower in January feels backwards, with the tomatoes in full swing and the hose out every evening.
It works because a brassica builds its leaves first and its head second, and leaves grow quickly in warm weather.
Why the slow brassicas start in midsummer
Size before the cold is the point. As autumn days shorten, growth slows to a crawl, and the head, curd or sprouts fill from whatever leaves the plant has built.
From sowing, cauliflower takes 12 to 22 weeks, broccoli 10 to 16 and kale 7 to 10. Cabbage takes 8 to 20 weeks by type, Brussels sprouts 11 to 16 after planting out. Our broccoli guide and cabbage guide name quick and slow varieties.
Work backwards from your first frost
- Note the month your first frost usually arrives. Our guide to what to sow in autumn shows how to find it.
- Count back two months: slow crops should be planted out and growing by then.
- Count back four to six weeks more for the tray stage, and sow.
- Add the weeks to maturity, from sowing or planting out as the packet says, plus two to four for slow autumn growth, to find the harvest.
Brussels sprouts need about five months from sowing, so follow the table for them.
With a mid-April frost, cauliflower sown in early to mid January is planted out by mid-February, and curds follow from mid-April to midwinter. Frost-free gardens work to heat at both ends instead.
When to sow each brassica in your zone
Sowing months from the Happy Valley Seeds calendar. For everything else that goes in during January, see what to sow in January. For a winter crop, use the summer and autumn months of each window.
| Zone | Broccoli | Cabbage | Cauliflower | Brussels sprouts | Kale |
|---|---|---|---|---|---|
| Tropical | Apr to Jul | Apr to Jul | Apr to May | Not recommended | Apr to Jun |
| Subtropical | Feb to Jun | Mar to Aug | Mar to Apr | Dec to Feb, marginal | Mar to Jun |
| Arid and semi-arid | Feb to May | Mar to Sep | Feb to May | Jan to Feb | Mar to Jun, Aug |
| Temperate | Jan to May, Aug to Sep | Aug to Mar | Aug to Mar | Dec to Jan | Jan to May, Aug to Sep |
| Mediterranean | Mar to Jul | Feb to Sep | Dec to May | Dec to Jan | Feb to May, Aug to Sep |
| Cool and alpine | Sep to Feb | Sep to Feb | Aug to Feb | Nov to Dec | Sep to Mar |
Tropical (Darwin and the Top End in the Northern Territory, Cairns and Townsville in Queensland, the Kimberley in Western Australia): skip the summer start and sow from April, as the wet eases and nights cool.
Subtropical (Brisbane and south-east Queensland, northern New South Wales): start broccoli in shaded trays in February, and cabbage, cauliflower and kale in March.
Arid and semi-arid (Alice Springs in the Northern Territory, Broken Hill in New South Wales, Mildura in Victoria, Kalgoorlie in Western Australia): sow broccoli and cauliflower from February, cabbage and kale from March, as nights cool. Brussels sprouts, sown under shade in January and February, suit southern districts with frosty winters.
Temperate (Sydney and the New South Wales coast, Melbourne in Victoria): January is the last month for Brussels sprouts, and broccoli planted out by Anzac Day heads through winter.
Mediterranean (Perth and southern Western Australia, Adelaide in South Australia): broccoli waits for March. Check shaded trays twice a day in the dry heat.
Cool and alpine (Tasmania, Canberra in the ACT, Ballarat in Victoria, Orange and Armidale in New South Wales, Stanthorpe in Queensland): February closes most windows, and Brussels sprouts do best sown in November or December, so plants establish before hard frosts.
The zones are broad groupings. Between two, go by your own first frost and January heat.
Germination temperatures and heat
Our guides give germination ranges of 7 to 30°C for broccoli and Brussels sprouts, 8 to 30°C for kale, 10 to 30°C for cauliflower and 7 to 35°C for cabbage, and in summer warmth most come up within a week.
Above those ranges germination falls away: University of California tables put the limit for cabbage and cauliflower at about 35 to 38°C. Near the ground, full sun runs hotter than the forecast: in Western Australian wheatbelt heatwaves, Greening Australia recorded up to 54°C at seedling height when the air peaked at 46°C.
Raising seedlings in the heat, step by step
- Use cell trays of damp seed-raising mix, such as our 72 cell seedling tray, so each seedling keeps its root ball and the tray can be moved. Potting mix can carry Legionella bacteria, so wear gloves and a mask, then wash your hands, as healthdirect advises.
- Find bright shade: morning sun and afternoon shade, or 30 to 50% shade cloth. On a heatwave day, bring trays indoors.
- Sow in the evening, 5 to 10 mm deep, two seeds to a cell, and water well, so the seed drinks through the cool night.
- Keep the mix damp, checking morning and evening, and stand a drying tray in water for a few minutes: one dry spell can kill a seedling.
- Mesh the tray once seedlings show, as butterflies lay on them too.
- Thin and feed: snip out the weaker seedling at the first true leaf, then give half-strength fish and seaweed liquid every week or two.
- Plant out at four to six weeks, before roots circle the cell.
Hardening off and planting into hot ground
In summer, hardening off is about sun and wind, not cold: over a week or so, give the tray longer in morning sun each day, as our hardening off guide describes.
- Soak the bed the day before, and water the tray an hour before planting.
- Plant late on a mild or overcast afternoon, at packet spacing, a little deeper than the seedling grew.
- Water in and draw straw mulch around each plant, clear of the stem, to keep the soil cooler.
- Shade for a few days: mesh on hoops cuts a little sun, and shade cloth can top it in a hot spell.
A wilt on hot afternoons and a pause of a week or two are normal, but water any plant still limp at dawn. Our planting out guide has more.
Fine mesh from day one
Summer seedlings grow up while the cabbage white butterfly (Pieris rapae) is active, and in warm weather the diamondback moth (Plutella xylostella) can go from egg to moth in about two weeks. The moth also resists many insecticides, so exclude both rather than spray.
Use insect exclusion mesh with holes of about 1 mm or finer, not bird netting: in Canadian government trials, meshes from 0.6 to 1.3 mm all cut caterpillar numbers on broccoli. Check for eggs, then stretch the mesh over hoops and weigh down every edge, as in ABC Gardening Australia's DIY netting tunnel. Our cabbage white caterpillar guide covers back-up options.
Buttons and bolting
- Buttoning, or premature heading, is a coin-sized head on a plant too small to feed it, set off by heat, drought, hunger, cold or an overgrown transplant. The button does not grow on.
- Heading in heat spoils the crop. Broccoli bolts, opening into yellow flowers within days, cauliflower curds turn loose, and cabbage heads can split, as they also do after uneven watering or late picking. Timing is the main fix.
See our guides to cauliflower head problems and cabbages not forming heads.
Frequently asked questions
Can I sow brassicas straight into the garden in January?
You can, but a sunny seedbed dries and heats faster than a shaded tray. Shade the row, keep it damp and mesh it at once.
Is February too late for Brussels sprouts?
Usually, in Temperate, Mediterranean and Cool and alpine gardens, though Peter Cundall's Tasmanian guide allows a late February sowing. Arid gardens with frosty winters can still sow, and subtropical gardens can try. If you have missed it, grow cabbage or kale.
What shade cloth suits brassica seedlings?
About 30% most days and 50% in a hot spell. Heavier cloth left on for weeks makes seedlings leggy.
My seedlings are tall and floppy. Can I still plant them?
Yes. Bury the stem to just below the seed leaves for support, and give the next tray more light, as our leggy seedlings guide explains.
A well-timed tray of sturdy seedlings is a fine start to the winter vegie patch.
Related growing guides
- Netting crops and fruit: exclusion nets, fruit bags and wildlife-safe mesh
- What to sow in January: vegetables for every zone
- What to sow in December: vegetables for every zone
- Plan a year in the vegie patch
- What to sow in autumn in Australia
- How to grow Brussels sprouts in Australia
Pick your winter crop from our broccoli seeds and cauliflower seeds.