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Kale

Brassica oleracea (Acephala group)

VegetableLeafy greenCool-seasonBeginner Easy

Hardy and productive, and sweeter after a frost. Heat — not cold — is its real limit, so the fall crop is the best. Pick the outer leaves and leave the central growing point intact.

Growing conditions

Light
Full sun — about 6 or more hours of direct sun for fast, sturdy growth; tolerates part shade (4–6 hours), and light afternoon shade is welcome where summers are hot
Water
Medium
Soil
Fertile, well-drained loam rich in organic matter; works compost in before planting. Kale is a moderate feeder that wants steady moisture and won't thrive in compacted or waterlogged soil. · pH 6.0–7.5, with 6.5–6.8 ideal; near-neutral to slightly alkaline soil also suppresses clubroot
When to sow
For spring, transplant or direct-sow about 4–5 weeks before the average last spring frost — kale shrugs off light frost as a young plant. For fall (the sweeter, more reliable crop), sow about 3 months (roughly 10–12 weeks) before the average first fall frost so plants size up before hard cold, then keep harvesting through repeated frosts.
Spacing
30–45 cm (12–18 in) between full-size plants in rows 45–90 cm (18–36 in) apart; for baby-leaf cut-and-come-again, sow much denser at about 7.5–10 cm (3–4 in)
Days to maturity
25–35 days for baby leaf; about 50–65 days for full-size leaves from transplant, or roughly 60–80 days from direct seeding
Hardiness
Grown across USDA zones 2–11 as a cool-season crop, and one of the hardiest garden vegetables — established plants survive into the teens °F (about -12°C), and many overwinter under mulch or cover. Time it to the cool windows: zones 2–6 grow it spring and (best) late summer into fall; zones 7–8 spring, fall, and through winter with light protection; zones 9–11 grow it fall through early spring and skip the summer heat.

How to grow it

  1. 1

    Sow shallow, then thin (or transplant)

    Drop seed 0.6–1.3 cm (1/4–1/2 in) deep into firmed, -enriched soil and keep it evenly moist; it will within about a week. For an early start you can sow indoors, off the seedlings over about a week, and . Thin direct-sown plants to 30–45 cm (12–18 in) so each one has room to bush out.

  2. 2

    Water deeply and keep it even

    Aim for about 2.5 cm (1 in) of water per week, and deep water at the base rather than splashing the leaves. Steady moisture keeps the leaves tender and mild; drought stress makes kale tough, bitter, and quicker to in heat.

  3. 3

    Mulch to keep roots cool and clean

    Lay 5–7.5 cm (2–3 in) of straw or shredded-leaf around the plants. Mulch holds moisture, keeps soil cool to slow in late spring, suppresses weeds, and keeps grit and soil-splash off the lower leaves you'll be eating.

  4. 4

    Feed for leafy growth

    Kale is grown for its leaves, so it appreciates nitrogen. Mix in before planting, then side-dress or with a balanced or nitrogen-leaning feed a few weeks after and again midway through the season to keep new leaves coming.

  5. 5

    Cover up to outsmart the bugs

    The cabbage family draws cabbage worms, loopers, flea beetles, and aphids. Float a lightweight row cover over the bed right after sowing or and seal the edges, so the moths and beetles can't reach the plants in the first place. Scout the undersides of leaves weekly and hand-pick green caterpillars; use Bt (Bacillus thuringiensis) if they get ahead of you.

  6. 6

    Harvest the outer leaves, cut-and-come-again

    Once plants are about 20–25 cm (8–10 in) tall, snap or cut the lowest, outermost leaves first — roughly a fist's worth (3–5 leaves) per plant per picking — and always leave the central growing bud and the small inner leaves untouched. That crown keeps pushing out fresh leaves for weeks or months.

  7. 7

    Stretch the season with succession and cold

    For a steady supply, -sow a short row every few weeks in spring and again in late summer for fall. In cold zones, let plants keep standing — a , cold-hardy curly type will hold in the garden through hard frosts and often into winter as a living larder.

Gardener's notes

  • Frost is a feature, not a danger: a couple of hard fall frosts make kale measurably sweeter by turning stored starch into sugar — so the best-tasting kale comes from the cold end of the season, not summer.
  • Cut only the outer leaves and never the central growing point — that crown is what keeps a single plant cropping for months. Topping it ends the harvest.
  • Summer heat, not cold, is what ruins kale — above about 24°C (75°F) the leaves turn tough and bitter and plants are quicker to , which is why US extension services push the fall crop over the spring one.

Varieties worth knowing

Winterbor / Darkibor (F1, curly)
Curly type — tightly ruffled blue-green leaves on tall, vigorous, very cold-hardy plants; a workhorse for fall and overwintering, about 55–65 days.
Lacinato / Toscano (also called Dinosaur or Tuscan)
Lacinato type — long, narrow, deeply savoyed (bumpy) dark blue-green strap leaves; an Italian heirloom prized for flavor, roughly 30 days baby / 60 days full.
Red Russian
Red Russian type — flat, oak-shaped, toothed gray-green leaves with purple stems and veins; one of the most tender and sweet kales, great for baby leaf and bunching, about 25 days baby / 50 days full.
Dwarf Blue Curled Vates
Curly type — compact, low-growing, finely curled blue-green; a dependable, very cold-tolerant heirloom for small gardens.
Redbor (F1, curly)
Curly type — deep magenta-purple ruffled leaves that intensify in cold; ornamental and edible, equally at home in beds and borders.

Common problems & fixes

Cabbage worms & cabbage loopers
Sign: Velvety green caterpillars (imported cabbageworm) or inch-worm-style loopers chewing ragged holes and leaving dark green-black frass (droppings) on the leaves.
Fix: Exclude the white/brown moths with row cover, hand-pick caterpillars and eggs, and spray Bt (Bacillus thuringiensis) or spinosad — both target caterpillars while sparing most beneficial insects. A few holes are cosmetic; act when leaves are being skeletonized.
Cabbage aphids
Sign: Dense clusters of waxy gray-green aphids tucked in the growing tip and leaf folds, with curled, distorted leaves and sticky honeydew.
Fix: Blast them off with a hard spray of water, squash colonies, and use insecticidal soap on the undersides. Invite ladybugs and hoverflies with flowering companions, and always check inside crinkled leaves before eating — these aphids hide deep.
Flea beetles
Sign: Dozens of tiny round 'shothole' pits in the leaves, worst on young plants; the shiny black beetles hop away when disturbed.
Fix: Floating row cover from day one is the best defense. Keep seedlings vigorous with good water, use kaolin clay or insecticidal soap if needed, and clean up garden debris where beetles overwinter. Established plants usually outgrow the damage.
Clubroot
Sign: Plants wilt in the heat of the day, grow stunted and yellow, and the roots are swollen into gnarled, club-like galls.
Fix: There's no cure once soil is infested — the spores last 10+ years. Prevent it: rotate brassicas on a 3–4 year cycle, improve drainage, and lime the soil to raise pH to about 7.2, which blocks the spores from infecting roots. Never move infested soil or transplants to clean beds.
Black rot
Sign: Yellow V-shaped lesions spreading inward from leaf margins, with blackened veins; the bacterium spreads in warm, wet, splashy weather.
Fix: Start with clean, hot-water-treated seed, rotate away from brassicas, avoid overhead watering and working among wet plants, and remove and destroy infected plants and debris.

Companions

Grows well with
Onions, garlic and chives (their scent deters aphids and cabbage pests)Aromatic herbs like dill, rosemary, thyme and mintNasturtiums (trap crop for aphids)MarigoldsBeets and other root cropsBush beans (fix nitrogen for this leafy feeder)
Keep apart from
Other brassicas like cabbage, broccoli and cauliflower (share pests and diseases, and compete as heavy feeders)StrawberriesPole beans (climb and shade in tight beds)Tomatoes and other heavy feeders that compete for nutrients

Harvest & storage

Harvest
Begin once plants are about 20–25 cm (8–10 in) tall. Harvest as cut-and-come-again: take the lowest, oldest outer leaves — roughly 3–5 per plant at a time, hand-sized or smaller — and leave the central bud and inner leaves so the plant keeps producing for months. Pick baby leaves whole at 25–35 days. Harvest in the cool of morning. Above all, kale is at its sweetest after a few fall frosts, which convert starches to sugars, so the cold-season crop is the prize one.
Storage
Kale doesn't cure or keep long. Don't wash it until use; wrap unwashed leaves loosely in a damp towel or perforated bag and refrigerate at about 0–2°C (32–36°F) and high humidity, where it holds for about 1–2 weeks (a touch longer for fresh, dry-picked leaves). For months of storage, blanch and freeze the leaves. Keep kale away from ethylene producers like apples and tomatoes, which yellow it faster.

Sources

This guide is curated from authoritative horticulture references — primarily US university Extension services, the USDA, and the RHS.