How to Grow Kale: From Sowing to a Winter's Worth of Harvests

If you only grow one vegetable for the cold half of the year, make it kale. It shrugs off frost and snow, it gets sweeter as the weather gets colder, it is far too tough for most of the diseases that flatten its cabbage cousins, and it works on a cut-and-come-again basis for months on end: you never harvest a kale plant, you just keep borrowing leaves from it. Here is the full calendar, from seed packet to the last sweet spring shoots.

Choosing a variety

Sowing: a long, forgiving window

The main sowing window runs from mid-spring to midsummer. Sow 1 cm deep, either in a seedbed outdoors or — easier and safer from slugs — two seeds to a module in trays, thinning to the stronger seedling. Kale germinates fast and reliably in warm soil, often inside a week. For winter and spring harvests, a late-May to July sowing is the sweet spot: the plants reach a good size by autumn, then stand through the cold months. Missed it? In early autumn you can still sow fast-growing kale as baby salad leaves in a cold frame, greenhouse border or a deep tray on a bright windowsill, picking small tender leaves within five to six weeks — and in mild-winter regions, September transplants of young plants will crop modestly through winter.

Planting out

Move seedlings to their final position when they have four to six true leaves. Kale wants what all brassicas want: fertile, moisture-retentive soil that has been firmed well — loose, fluffy soil produces loose, rocking plants — in full sun, though it tolerates light shade better than most vegetables. Space plants about 45 cm apart each way for full-sized plants, or as close as 25 cm if you plan to keep them small and pick baby leaves. Plant deeply, burying the stem up to the first leaves, water in well, and keep plants watered through any dry spells in summer; consistent moisture is what keeps leaves tender rather than leathery.

Tip: kale is one of the best vegetables for containers. One plant per 30 cm pot of rich compost on a sunny balcony will supply leaves for months — and a pot of 'Redbor' looks better than most ornamental grasses while doing it.

The two enemies: caterpillars and pigeons

Kale's problem list is short but non-negotiable. From early summer, cabbage white butterflies seek out every brassica in the neighbourhood to lay eggs on, and their caterpillars can skeletonise a young plant in days. From autumn into winter, hungry pigeons treat unprotected kale as a bird table. The answer to both is the same and it is not a spray: fine insect netting or butterfly netting over hoops from the day you plant, sealed at the edges. Check under leaves for the yellow egg clusters and rub off any you find. Grey cabbage aphids and whitefly sometimes colonise leaf undersides in warm weather — blast them off with a hose or use insecticidal soap, and note that the first hard frosts largely end the problem for you.

Warning: like all brassicas, kale should not be grown in the same bed as last year's cabbages, broccoli or Brussels sprouts. Rotating brassicas around the garden on a three- to four-year cycle is your main protection against club root, a soil disease that persists for years once established and stunts every brassica that follows.

Harvesting: borrow, never behead

Start picking as soon as plants are established and leafy. Work from the bottom of the stem upwards, snapping or cutting the older outer leaves and always leaving the central rosette of young leaves at the top to keep producing. A handful of leaves per plant per week is sustainable for months; the plant slowly grows a bare, palm-like trunk as the harvested zone rises. Baby leaves for salads can be picked at 5–10 cm. And do not rush to harvest before the cold arrives: frost triggers kale to convert stored starches into sugars — natural antifreeze — which is why the same leaf genuinely tastes sweeter and nuttier in December than it did in September.

The spring bonus

Plants that stand through winter aren't finished. In early spring, overwintered kale throws out clusters of tender new side shoots and immature flower buds — treat them like sprouting broccoli, picking them before the yellow flowers open, and you get several weeks of the sweetest harvest of the whole cycle. Once plants finally bolt in mid-spring, clear them for the compost heap (roots and all, to be safe with club root) and the bed is free for summer crops.

Spotted holes, grey clusters or mysterious wilting on your kale and not sure who to blame? Photograph the leaf in PlantMe — the Plant Doctor is trained on 500+ plant diseases and problems and will separate caterpillar damage from slug damage, and hungry-plant yellowing from something that needs action, in seconds.