Kale is the vegetable that ignores the calendar. Long after the courgettes have collapsed and the last beans have been pulled, a row of kale stands out there in the frost, quietly getting better. Its botanical name gives the game away: Brassica oleracea var. acephala — headless cabbage. Where a cabbage packs everything into one dense head and then it is over, kale keeps its leaves open on a lengthening stem and hands them to you a few at a time, from October to April.
That difference is not a botanical footnote. It decides when you sow, how far apart you plant, how you feed, and above all how you pick. This guide covers the full cycle: the late-spring sowing window most gardeners miss, planting out deep and firm so winter gales cannot rock the plants, the real difference between curly kale and cavolo nero, and the harvesting rule that keeps one plant productive for eight months instead of eight weeks.
- Sow April–June in modules; May is the sweet spot
- Plant out 45–60 cm apart, deep and very firm
- Harvest October–April, lower leaves first
- Watch for cabbage white caterpillars, pigeons, clubroot
Why kale keeps going when everything else stops
A kale plant does not build a harvest and then hand it over. It builds a stem. Each week it adds leaves at the top and you take leaves from the bottom, and provided you never touch the growing point, that exchange can run from autumn until the plant runs to flower the following spring. It is the closest thing the vegetable garden has to a tap.
Hardiness is the other half of the story. Most named varieties shrug off −10 °C and the curly types go colder still. Frost also improves the flavour — the plant converts stored starch into sugars as a natural antifreeze, which is why kale cut in January tastes sweet and kale cut in September tastes like a lawn. We explain the mechanism in more detail in our cabbage growing guide, and it applies to the whole leafy brassica family.
When to sow kale — and why May is the sweet spot
For full-size winter kale, sow between April and June. May is ideal. The plant needs roughly fourteen to sixteen weeks of decent growth to build a stem and a root system before the light collapses in November, and everything it produces from December onwards is drawn on reserves banked before then. A plant sown in May is knee-high and cropping by October. The same seed sown in August makes a teacup-sized rosette that sits there all winter doing nothing much at all.
There are two useful exceptions. Sown thickly and cut at 10–15 cm, kale makes an excellent cut-and-come-again salad leaf from any sowing between April and September. And as a microgreen on a windowsill it can be sown in any month of the year — several varieties in our microgreens range are sold specifically for this. Browse everything you can sow this spring in the April and May sowing collections, or check the vegetable sowing calendar for the whole year.
Sowing kale, step by step
- Sow into modules, not open ground One or two seeds per cell, 1.5 cm deep, in ordinary multipurpose compost. Modules keep the roots intact at transplanting and keep young plants off slug-level for their first six weeks.
- Germinate at 15–20 °C Seedlings appear in 5–8 days. Kale is not fussy about warmth — a shaded cold frame or an outdoor bench in May is fine. See our indoor seed starting guide if you are sowing under cover.
- Thin to one and grow on cool and bright Snip the weaker seedling rather than pulling it. Warm and dim gives you a leggy, floppy plant that never quite recovers.
- Harden off for 7–10 days Even a hardy brassica sulks if it goes straight from a bench to open ground. Our hardening off guide covers the routine.
- Plant out at four to six true leaves Usually five to six weeks after sowing, when the plant is 10–15 cm tall. Water the modules an hour beforehand so the rootball slides out whole.
Planting out: deeper and firmer than feels right
Picture a kale plant in February: a 70 cm stem with a sail of leaves on top, in a gale, in wet ground. Everything you do at planting time is insurance against that image.
Plant deep — bury the stem up to the lowest pair of leaves. Brassicas root readily from buried stem tissue, so you gain anchorage and a second set of roots for nothing. Then firm hard: knuckles or the heel of your boot, until the soil is properly compacted around the stem. The old allotment test still works — tug a leaf, and if the plant lifts, you have not firmed enough. Soil that has just been dug is the worst possible seedbed for a brassica; tread it before you plant, and read our soil preparation guide for what a firm, fertile brassica bed actually needs.
Space plants 45–60 cm apart. Cavolo nero is upright and manages at 45 cm; a big curly variety wants the full 60. It looks absurdly generous in June and exactly right in December, when air movement between plants is the difference between clean leaves and grey mould. Give the bed a fresh position each year — crop rotation is the main defence against clubroot, and kale should not follow cabbage, mustard greens or turnips. In autumn, draw soil up around the stems and stake anything over 60 cm.
Curly kale or cavolo nero?
Curly kale (Westland Autumn, Winterbor F1, Scarlet)
The hardiest thing in the winter garden.
- Tightly frilled leaves trap air and survive hard frost unbothered
- Those frills also trap grit and rain — wash properly before cooking
- Sweetest of all after a freeze; the classic choice for winter greens and crisps
Cavolo nero (Nero di Toscana, black palm)
Upright, architectural, and far quicker to prepare.
- Long, blistered strap leaves on a stem that reaches 90 cm
- Clean to pick and strip; the right texture for soups, ribollita and pasta
- A shade less hardy — give it the sheltered end of the bed
Red varieties such as Scarlet sit between the two: curly-leaved, deep purple, and they colour up most intensely in cold weather, which makes them worth a place at the front of a bed. Tronchuda types are different again — broad, flat, cabbage-like leaves on a plant grown as much for the thick midribs as the blades. You will find all of them in the kale collection, with certified options in organic kale.
Picking: from the bottom, never the top
This is the one rule that separates a kale plant that feeds you until April from one that gives up in November. The growing point sits at the very top of the stem, and it is the plant. Cut it out and nothing more is produced; all you can do afterwards is strip what is left.
So harvest from the bottom. Take two to four of the lowest usable leaves from each plant per week, snapping them downwards and outwards so they come away cleanly at the stem. Always leave at least six to eight leaves at the top — that is the plant's engine. Start once leaves reach the size of your palm, but if you can wait until after the first proper frost, do; the flavour is a different vegetable altogether. Any lower leaves that go yellow should come off at the same time and go on the compost heap, because a wet yellowing leaf against a stem in December is exactly where grey mould starts.
There is a final bonus most gardeners never see, because they pull their plants too early. Left in the ground, kale is biennial: the following April it bolts and throws up flowering shoots. Picked young, before the buds open, those sprouting tops are the sweetest, most tender thing the plant ever makes — treat them like purple sprouting broccoli. Take a fortnight of those, then pull the plant and put the bed to another use.
Common mistakes
- Sowing in late summer for a winter crop. There is not enough light left. Sow in May for winter kale, and use late sowings for baby leaf only.
- Planting into loose, freshly dug soil. Wind rocks the stem, the roots tear, and the plant stalls. Firm hard.
- Picking the top. Removing the growing point ends production for good.
- Crowding at 30 cm. It looks efficient in summer and breeds mildew and mould all winter.
- Skipping the net. Cabbage white caterpillars can strip a plant in days, and pigeons finish the job in January. Fine mesh over hoops from planting until the first frosts solves both — see common garden pests.
Frequently asked questions
Can I sow kale in September?
Not for a winter crop — there is too little light and warmth left for the plant to build anything before spring. September sowings are worth it only as microgreens or baby leaf under cover, cut small. For proper winter greens sown now, look instead at winter lettuce, corn salad and the other crops in our what to sow in September guide.
Is kale a perennial?
Botanically it is a biennial: leaves in year one, flowers and seed in year two. Most gardeners grow it as an annual and pull it in spring, but leaving a plant to produce sprouting tops in April is well worth doing before you clear the bed.
Why is my kale tough and bitter?
Usually heat and age. Leaves grown through a hot spell, or left on the plant far too long, turn coarse and bitter. Pick regularly rather than waiting for leaves to reach maximum size, and remember that cold weather is what converts the starch to sugar. A drought-stressed plant is bitter too, so water in dry spells and feed with a balanced liquid feed in mid-summer — our feeding guide explains what to use when.
Can I grow kale in a container?
Yes, but give it a big one — at least 30 cm across and 30 cm deep per plant, in a heavy loam-based compost that will not blow over. Feed fortnightly from midsummer, since a pot holds very little. See container gardening from seed and browse container-friendly vegetables.
Kale earns its space by being useful in the months when the plot has nothing else to offer, so it belongs in a bed you can reach in the rain, near the spinach and chard that carry the same season. Once it is planted and netted, the rest of the brassica year plans itself — broccoli, Brussels sprouts and the wider cabbage family all want the same firm, rotated ground. And while the kale looks after itself outside, the glass is the job that needs doing now: see how to clean a greenhouse in autumn. Browse the full Brassica oleracea range, our organic vegetable seeds and everything else in vegetables, or work through the rest of our growing guides.
