Vegetable · Brassicaceae
Kale
Brassica oleracea Acephala Group
Deep green and heavily crinkled, kale yields tender leaves from spring right through winter.
Full sun
Every 3–7 days
55–75 days
USDA 2–11
Overview
Kale is a leafy member of the cabbage family that never closes into a head, opening instead into a loose rosette of leaves that spray outward from a central stalk. Up close the foliage swings from tightly ruffled blue-green curls in the standard types to long, puckered, strap-shaped blades in the Italian heirlooms, their surfaces dimpled and blistered like worked leather. For all that texture, it is among the easiest vegetables a beginner can grow.
This is a cool-season crop, at its finest in the mild weather of spring and fall, and its thick, waxy leaves stand firm through frost that limps a tomato. The cold does the plant a favor, since a hard chill sweetens and softens the leaves rather than coarsening them.
Set in full sun with steady moisture and rich soil, kale builds a wide, low fountain of leaves that keeps feeding you for months. You strip the broad outer blades as you need them and leave the tight center to unfurl more, so the plant offers up a fresh flush of leaves again and again instead of a single crop.
Care
The short version: kale wants full sun and rich, evenly moist soil with about an inch to an inch and a half of water a week. Feed it through the season, plant it for spring and again for fall, and strip the lower leaves as they broaden.
Light
Kale wants full sun, at least 6 hours a day, to pack its rosette full of broad, deeply colored leaves. It will grow in partial shade, useful where summer heat is strong, though deep shade thins the plant out and leaves it slow with sparse, pale foliage.
Water
Keep the soil evenly moist with about 1 to 1.5 inches of water a week. Steady moisture is what keeps the crinkled leaves tender and mild rather than tough and bitter, so a layer of mulch to hold the moisture in is worth laying down.
Soil
Plant kale in fertile, well-drained loam worked through with plenty of organic matter. A pH of 6.0 to 7.5 suits it, and lifting acidic soil toward the top of that range also helps hold clubroot at bay.
Temperature
This cool-season crop holds across a wide band of 10°F to 81°F (-12°C to 27°C). The thick leaves take hard frost in stride and even sweeten in the cold, while real summer heat turns them bitter and sends the plant shooting up to bolt.
Humidity
Ordinary outdoor humidity is all kale asks for, so there is no figure to reach for. Good airflow counts for more, since crowded, damp leaves packed close invite the aphids and diseases that trouble brassicas.
Feeding
Work a balanced fertilizer into the bed at planting, guided by a soil test, then side-dress with nitrogen about 4 to 6 weeks later to keep new leaves unfurling. Hold back on the nitrogen, or the soft, lush growth it forces draws aphids.
Pruning
Kale needs no real pruning. Harvest the lower, outer leaves once they are broad but still tender, leave the tight central growing point untouched so the plant keeps producing, and pull off any leaf gone yellow or chewed.
Size & spacing
Plants stand 1 to 3 feet (30 to 100 cm) tall and spread nearly as wide into a low, leafy dome. Set them 12 to 18 inches (30 to 45 cm) apart so air moves between the leaves and each plant has room to fill out.
When to plant
Kale is made for cool weather and a long season. Sow it in early spring for an early summer cutting, then sow again in midsummer for a fall and winter crop whose leaves only sweeten as the cold deepens.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Start seed indoors 6-8 weeks before the last spring frost; for a fall crop, start in mid-summer
- Plant: Set transplants out 3-4 weeks before the last spring frost, or direct sow as soon as soil is workable; sow again in mid- to late summer for fall harvest
- Harvest: Harvest spring sowings in late spring to early summer before heat turns leaves bitter; harvest fall crops into winter - flavor sweetens after light frosts
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most of kale's troubles show plainly on the leaves, in the ragged holes, curling, and pitting that the chewing and sap-feeding pests leave behind. Turn the leaves over and study the undersides often to catch the signs early. Match what you see below, then act before the damage spreads.
Plants wilting and stunted with swollen, distorted roots
Leaves that go limp in the afternoon sun, then yellow while the plant stalls, call for a look below the soil line. Thick, swollen, club-shaped galls twisting the roots are clubroot, a soilborne disease with no cure once it has taken hold, while roots left tunneled and chewed around small white grubs are the work of cabbage root maggot. Lift and destroy anything affected rather than composting it, shift the brassicas to fresh ground, and lime the old bed toward pH 7.0 or above.
Fix:
- Remove and destroy infected plants; do not compost them
- There is no cure in infested soil - grow brassicas elsewhere
Ragged holes chewed through the leaves
Torn holes with a scatter of green droppings below them betray cabbageworms and cabbage loopers, the velvety green caterpillars that press flat against the leaf underside, often joined by diamondback moth larvae. Pinch the caterpillars off by hand, then reach for Bt or spinosad if fresh ones keep appearing. A floating row cover draped over the plants at transplanting stops the pale, fluttering moths from laying their eggs.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) or spinosad according to label directions
Curled, sticky leaves with clusters of small insects
Dense, waxy gray-green colonies wedged into the crimped folds of the leaf are cabbage aphids, their coating giving the cluster a dusty, powdered look. A hard jet of water breaks the colony apart, and insecticidal soap worked into the undersides, where they hide, finishes them. The lady beetles and parasitic wasps that patrol the leaves keep the next generation down, so they earn their place.
Fix:
- Dislodge with a strong spray of water
- Apply insecticidal soap, covering leaf undersides thoroughly
- Encourage natural enemies such as lady beetles and parasitic wasps
Tiny shothole pits peppering young leaves
A fine peppering of tiny round pits across the tender young leaves is the mark of flea beetles, glossy black specks barely larger than a grain that spring off the moment a shadow falls. They work hardest on seedlings during warm, dry spring weather and seldom trouble a plant already growing strongly. Held under row cover and pushed to grow fast, the young leaves fill in past the pitting.
Fix:
- Protect young plants with row cover
- Apply a labeled insecticide if damage is severe on seedlings
Toxicity
Kale is a food crop from leaf tip to stalk, safe for people and for the animals around the garden. No toxin runs through the plant, so the only real note is moderation: very large amounts of the raw brassica foliage, fed day after day, can act as a mild goitrogen for grazing livestock.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The crimped green leaves hold no toxin for cats, so a curious nibble does no harm. A cat that tears through a whole pile of the raw foliage might get a little gas or a soft stool, and that is the extent of it.
Dogs None
Plain kale is safe for dogs and turns up chopped into many home-cooked bowls. The portions stay small, since a sudden heap of the coarse raw leaves can leave a dog gassy or briefly upset.
Horses Safe
The leaves pose no poisoning risk to horses. They belong as an occasional handful rather than a staple, because a steady diet of the brassica foliage acts as a mild goitrogen over time.
Rabbits Safe
Rabbits crop the tender leaves as one green among a varied mix. Bring them in slowly and keep the helpings small so they never crowd out the hay a rabbit's gut depends on.
Livestock Safe
Cattle, goats, and sheep graze the leaves and stalks safely, and kale is grown on purpose as a forage crop. Fed as heaps of foliage day after day it acts as a goitrogen, so it balances against other feed.
Birds Safe
Chickens and other birds shred the leaves and peck at the thick stalk alike. Every part is a wholesome green treat with nothing toxic to avoid.
People Safe
The dark, crinkled leaves are a nutritious everyday vegetable, good raw in a salad or cooked down soft. A rinse under the tap comes first, as with any leafy green from the garden.
Like other brassicas, kale contains goitrogenic compounds; very large quantities of raw kale fed routinely could affect thyroid function or cause digestive gas in pets and livestock - a moderation note, not a poisoning risk.
Varieties
Dozens of kale cultivars exist, and they part company most clearly in the look of their leaves, from tight curls to flat straps and from blue-green to deep purple. A few show up again and again in gardens and on extension lists, and these are the ones worth knowing by name.
Lacinato (Tuscan, Dinosaur)
An Italian heirloom carrying narrow, dark blue-green straps of leaf, their surface so heavily puckered it looks pebbled and reptilian, and one UF/IFAS recommends for Florida gardens.
Winterbor
A very cold-hardy hybrid that stands tall and productive, its blue-green leaves tightly and finely curled at every edge.
Redbor
A curly hybrid in deep red-purple whose ruffled leaves darken further as the weather cools, ornamental enough for the flower bed as well as the kitchen.
Red Russian
One of the sweetest types, its leaves flat and toothed along the edge in soft gray-green, threaded through with purple veins on purple stems.
Vates Dwarf Blue Curled
A compact, low-growing curly standard with tightly ruffled blue-green leaves that resists bolting and has long been an extension favorite.
Companions
Kale grows best beside aromatic herbs and alliums that throw pests off the scent, and worst beside its brassica cousins, which trade the same diseases and pests back and forth.
Plant near
Dill: Aromatic herb whose flowers attract parasitic wasps and other beneficial insects that prey on cabbageworm and aphid pests of brassicas
Onion: Aromatic allium interplanted with brassicas may help confuse or deter common insect pests and competes little for space
Beet: Compatible cool-season root crop that occupies a different root zone and shares similar growing conditions without hosting brassica pests
Keep apart
Cabbage and other brassicas: Crops in the same family share pests and diseases (cabbageworms, aphids, clubroot, black rot); grouping them in the same bed and skipping rotation lets problems build up
Strawberry: Traditionally listed as a poor neighbor for brassicas; the perennial bed also conflicts with the crop rotation brassicas need
How to propagate
Kale is one of the simplest vegetables to start, rising readily from seed sown straight into the soil or raised as transplants.
SeedEasy
Direct sow in early spring as soon as soil can be worked and again in mid- to late summer for a fall crop, or start indoors 6-8 weeks before the last spring frost · Seed germinates in about 5-10 days; transplants reach setting-out size in 4-6 weeks and plants mature in roughly 55-75 days
Kale rises easily from small round seed, whether pressed straight into the bed or raised as transplants. Sow in early spring as soon as the soil can be worked, sow again in mid- to late summer for a fall crop, or start the seed indoors 6 to 8 weeks before the last frost. Set each seed 1/4 to 3/4 inch deep and stand the plants 12 to 18 inches apart. The first pale seedlings break the surface in about 5 to 10 days, reach transplanting size in 4 to 6 weeks, and mature in roughly 55 to 75 days.
Myths
Frost ruins kale, so the crop has to be done before cold weather arrives.
Kale is among the toughest vegetables in the garden, its thick, crinkled leaves standing firm through frost and light freezes that flatten tender crops. Cold pushes the plant to turn its starches into sugar, so the flavor sweetens rather than spoils after a frost. Fall and winter are when kale tastes its best.
The whole kale plant must be pulled to harvest it.
Take the large lower leaves and leave the central growing point at the top of the stalk untouched, and it keeps unfurling fresh ones. That way a single plant feeds you for weeks or months of repeat picking rather than one final cutting.