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Kale

The toughest vegetable in the garden, standing through frost and giving you greens right through winter.

1. Sow in a seedbed or modules 1.5 cm deep, then transplant, which gives stronger plants than direct sowing.
2. Firm the final bed by walking on it, then rake level.
3. Transplant when the seedlings have four or five true leaves, burying the stem up to the lowest leaves.
4. Space 45 cm apart each way and water in with a full can per plant.
5. Put fine insect mesh over the bed immediately and keep it there all season.
6. Fit a cardboard or felt collar around each stem at soil level against cabbage root fly.
7. Firm the soil around the stem again after storms, since loose brassicas rock and stop growing.
8. Start picking the lowest leaves once the plant is 30 cm tall, and keep picking all winter.

Soil

Firm, fertile, well-drained soil at pH 6.5 to 7.5. Brassicas want firm ground, so tread the bed before planting.

Sun

Full sun, though it tolerates half a day of shade better than cabbage does.

Water

About 15 to 20 litres per square metre per week in dry spells. Established plants are drought tolerant but the leaves get tough.

Spacing

45 cm apart, rows 45 to 60 cm apart

Depth

1.5 cm deep for seed, plant seedlings to the lowest leaves

Care

['Feed with a nitrogen-rich feed every three or four weeks until autumn, then stop.', 'Stake tall varieties such as the Tuscan types, which get top heavy and blow over.', 'Check under the leaves weekly for caterpillars and squash the eggs, which come in yellow clusters.', 'Strip off yellowing lower leaves so slugs and mildew have nowhere to sit.', 'Never pull the whole plant. Pick from the bottom and the top keeps growing.']

Harvesting

Pick the lowest mature leaves first, snapping them downwards, and always leave at least six leaves at the crown so the plant keeps going. Flavour genuinely improves after the first frost, which converts starch to sugar. In spring the flower shoots are the best part of the whole crop, picked like sprouting broccoli.

Storing

Keeps a week in a bag in the fridge. The real storage method is leaving it in the ground and picking as needed, which works even under snow. For longer keeping, blanch for two minutes, cool, drain and freeze for up to eight months. Kale also dries into crisps in a low oven.

Grow it next to

Good with beetroot, onions, potatoes, dill, mint and nasturtium as a trap crop for caterpillars. Keep away from strawberries and from other brassicas in the same bed, and never follow brassica with brassica.

Problems

[{'cause': 'Cabbage white butterfly caterpillars', 'fix': 'Fine mesh over the crop from planting out is the only reliable answer. Otherwise check leaf undersides weekly and rub off the yellow egg clusters.', 'symptom': 'Large ragged holes in the leaves and green caterpillars underneath'}, {'cause': 'Clubroot, a soil disease that lasts twenty years', 'fix': 'Lime to pH 7 or above, improve drainage, raise plants in large pots so they go out with a strong root system, and never grow brassicas on that ground again. Use resistant varieties.', 'symptom': 'Plants wilt in sun even when the soil is damp, and roots are swollen and distorted'}, {'cause': 'Mealy cabbage aphid', 'fix': 'Squash the colonies, remove badly affected leaves, and hose the plants down. Keep mesh on and clear old brassica stumps in spring, where the aphids overwinter.', 'symptom': 'Dense grey-white colonies on leaf undersides and distorted new growth'}, {'cause': 'Cabbage root fly larvae', 'fix': 'Fit a 12 cm collar of cardboard or roofing felt flat on the soil around each stem at planting, so the fly cannot lay next to the root.', 'symptom': 'Young plants wilt and die, with maggots at the root'}, {'cause': 'Loose soil around the stem', 'fix': 'Tread the soil firm around each plant, earth up the stem by 10 cm, and stake tall varieties.', 'symptom': 'Plants flop over and stop growing after wind'}]

Saving your own seed

Kale is biennial and must overwinter to flower. It is insect pollinated and crosses freely with cabbage, broccoli, cauliflower and Brussels sprouts, which are all the same species, so isolate by a kilometre or cage the flowers. Save from at least twenty plants.

Containers

Works in a 30 cm wide, 30 cm deep pot, one plant, or grow dwarf and baby-leaf varieties in a trough. Container kale needs a feed every two weeks and staking in wind.