General
Kale is a cold-hardy Brassica grown for nutrient-dense leaves. Curly kale (B. oleracea var. sabellica) forms frilly rosettes; Lacinato/palm kale (var. palmifolia) has long, blistered leaves and excellent winter flavor. Growth is best in cool weather (10–20°C) and leaves get sweeter after frost. In Sweden, kale is among the most winter-hardy vegetables and can often be harvested into winter, especially in sheltered spots or under a simple cover.
Light
Full sun to light partial shade; 6–8 hours of direct light gives best flavor and yields.
Soil type
Moisture-retentive, fertile loam with high organic matter; well-drained but not dry. Improve with compost. Slightly alkaline soil helps prevent clubroot.
Water requirement
Moderate, steady moisture. About 25 mm/week; more during hot, dry spells. Mulch to keep roots cool and even.
Nutrient requirement
High, especially nitrogen and calcium. Feed at planting and mid-season with compost or organic nitrogen sources.
Precultivation
Sow indoors in modules 4–6 weeks before planting out. Ideal germination 15–20°C; seeds sprout in 4–10 days. Cover seeds 0.5–1 cm deep. Transplant when seedlings have 3–4 true leaves. Harden off for 7–10 days before planting. For late-autumn/winter harvests, start an additional batch in late May–June.
Planting
Plant out when daytime temps are consistently above 5°C; kale tolerates light frost. Spacing: 40–50 cm between plants and 50–60 cm between rows (tighter for baby-leaf production). Plant slightly deeper, up to the first leaves, for stability. Water in well and mulch. Use insect netting immediately after planting to exclude cabbage butterfly, root fly, and flea beetles. Consider brassica collars to deter cabbage root fly.
Pruning
No true pruning required. Regularly remove yellowing lower leaves to improve airflow and reduce pests. For palm kale, harvest from the bottom up to maintain a single stem.
Maintenance
Keep soil evenly moist. Top-dress with compost or a light organic feed 4–6 weeks after planting. Mulch with straw, leaves, or grass clippings. Maintain pH 6.8–7.2; lime if soil is acidic to reduce clubroot risk. Keep beds weed-free. Use fine-mesh insect netting all season if pests are common. Hand-pick caterpillars; use biologicals (Bacillus thuringiensis) only if necessary. Beer traps or hand-picking for slugs. Avoid waterlogging in winter.
Harvest
Begin harvesting baby leaves when 10–15 cm long. For full-size plants, pick outer leaves as needed, leaving the center to continue growing. Frost improves sweetness; many varieties hold to −10 to −15°C, sometimes colder. In spring of year two, the plant sends up tender flower shoots (raab) that are excellent lightly cooked. Store leaves refrigerated in a breathable bag for up to a week; blanch and freeze for longer storage.
Common issues
Pests: cabbage white butterfly, cabbage moth, cabbage aphids, flea beetles, slugs, cabbage root fly. Prevention: insect netting, collars, trap crops (nasturtium), and timely harvest. Diseases: clubroot (favored by acidic, waterlogged soil) – rotate 4–6 years, raise pH to ~7.2, improve drainage, avoid brassica-heavy compost. Nutrient issues: pale leaves indicate nitrogen deficiency; interveinal chlorosis can signal magnesium deficiency—address with compost and balanced organic feeds. Bolting can occur in heat or drought; maintain even moisture.
Rotation schedule
Rotate Brassicas on a 4–6 year cycle. Do not follow or precede with other Brassicas (cabbage, broccoli, cauliflower, mustard, radish). Follow kale with legumes or alliums; precede kale with legumes or well-composted, fertilized beds.
Pollination
None needed (grown for leaves; flowering only in year two).
Companion plants
Onion family (onions, garlic, leeks), dill, chamomile, celery, nasturtium, marigold (Tagetes), mint (in containers), peas and beans to improve soil nitrogen.
Incompatible plants
Fennel, strawberries. Avoid planting near or after other Brassicas (cabbage, broccoli, cauliflower, mustard) to reduce disease and pest buildup.
