Vegetable · Brassicaceae
Kale
Brassica oleracea Acephala Group
Cold-hardy and generous, kale keeps giving 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 grown for its loose, open rosette of leaves rather than a tight head. It comes in a wide range of looks, from the ruffled blue-green curls of the standard types to the long, puckered straps of the Italian heirlooms. Tough and forgiving, it ranks among the easiest vegetables a beginner can grow.
This is a cool-season crop at heart. It does its best work in the mild weather of spring and fall, and it laughs off frost that would finish a tomato. Cold actually works in your favor here, since a hard chill turns the leaves sweeter and milder rather than tougher.
Give kale full sun, steady moisture, and rich soil, and one planting keeps feeding you for months. You pick the outer leaves as you need them and leave the center to grow, so the harvest stretches out instead of ending all at once.
Care
The short version: 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 pick the lower leaves as you go.
Light
Kale wants full sun, at least 6 hours a day, to grow full and leafy. It will get by in partial shade, handy where summer heat runs strong, but deep shade gives you thin, slow plants with sparse leaves.
Water
Keep the soil evenly moist with about 1 to 1.5 inches of water a week. Steady moisture is what keeps the leaves tender and mild rather than tough and bitter, so a layer of mulch to hold that moisture pays off.
Soil
Plant in fertile, well-drained loam worked over with plenty of organic matter. A pH of 6.0 to 7.5 suits it, and nudging acidic soil up toward the top of that range also helps keep clubroot at bay.
Temperature
This is a cool-season crop that thrives in the range of 10°F to 81°F (-12°C to 27°C). It takes hard frost in stride, and the cold even sweetens the leaves, while real summer heat turns them bitter and pushes the plant to bolt.
Humidity
Ordinary outdoor humidity is all kale asks for, so there's no number to hit. Good airflow counts for more, since crowded, damp leaves 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 the leaves coming. Don't overdo the nitrogen, or the soft, lush growth draws aphids.
Pruning
Kale needs no real pruning. Harvest the lower, outer leaves once they're large but still tender and leave the central growing point untouched so the plant keeps producing, and pull off any leaf that yellows or gets chewed up.
Size & spacing
Plants reach 1 to 3 feet (30 to 100 cm) tall and spread nearly as wide. Set them 12 to 18 inches (30 to 45 cm) apart so air moves freely between them and each one has room to fill out.
When to plant
Kale is built 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 that only gets sweeter as the cold sets in.
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 kale trouble lands on the leaves, where chewing pests and sap-suckers do their work in plain sight. Check the undersides often and you'll catch problems early. Match what you see below, then act before the damage spreads.
Plants wilting and stunted with swollen, distorted roots
When a plant wilts in the afternoon sun, yellows, and stalls, dig it up and look at the roots. Thick, club-shaped galls mean clubroot, a soilborne disease with no cure once it takes hold; tunneled roots with small white grubs point to cabbage root maggot instead. Pull and destroy infected plants, never compost them, and move brassicas to fresh ground while you lime the 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
These holes and the green droppings beneath them point to cabbageworms and cabbage loopers, often with diamondback moth larvae in the mix. Pick the caterpillars off by hand, then treat with Bt or spinosad if they keep coming. A floating row cover put on at transplanting stops the moths from laying eggs in the first place.
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 tucked into the leaf folds are cabbage aphids. Blast them off with a hard jet of water and follow up with insecticidal soap, making sure you hit the undersides where they hide. Lady beetles and parasitic wasps will keep the next wave in check, so leave them be.
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
The little round pits are the work of flea beetles, shiny black specks that spring away the moment you reach for them. They mostly trouble seedlings in warm, dry spring weather and rarely set a vigorous plant back for long. Keep young plants under row cover and growing fast, and they outpace the damage.
Fix:
- Protect young plants with row cover
- Apply a labeled insecticide if damage is severe on seedlings
Toxicity
Kale is a food crop through and through, safe for people and for the animals around the garden. There's no toxin to worry about, 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
Kale isn't toxic to cats, so a curious nibble does no harm. A cat that wolfs down a big pile of raw leaves might get a little gas or a loose stool, nothing more.
Dogs None
Plain kale is safe for dogs and shows up in plenty of homemade meals. Keep the portions small, since a sudden heap of the raw leaves can bring on gas or a mild stomach upset.
Horses Safe
Kale poses no poisoning risk to horses. Treat it as an occasional extra rather than a staple, because a steady diet of brassica greens can act as a mild goitrogen over time.
Rabbits Safe
Rabbits can eat kale as part of a varied mix of leafy greens. Introduce it slowly and keep the helpings modest so it doesn't crowd out their hay or upset a sensitive gut.
Livestock Safe
Cattle, goats, and sheep graze kale safely, and it is grown on purpose as a forage crop. Large amounts of the foliage day after day can act as a goitrogen, so balance it against other feed.
Birds Safe
Chickens and other birds enjoy pecking at kale, leaves and stalk alike. It makes a healthy green treat with no toxic parts to avoid.
People Safe
Kale is a nutritious everyday vegetable, good raw in a salad or cooked. Give it a rinse first, the way you would 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 are out there, but a few show up again and again in gardens and on extension lists. These are the ones worth knowing by name.
Lacinato (Tuscan, Dinosaur)
An Italian heirloom with narrow, dark blue-green, heavily puckered strap-like leaves that UF/IFAS recommends for Florida gardens.
Winterbor
A very cold-hardy hybrid that grows tall and productive, with finely curled blue-green leaves.
Redbor
A deep red-purple curly hybrid that earns its place in the flower bed as well as the kitchen, with color that deepens in cool weather.
Red Russian
One of the sweetest types, carrying tender, flat, toothed gray-green leaves with purple veins and stems.
Vates Dwarf Blue Curled
A compact, low-growing curly standard 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, growing readily from seed sown straight in the ground 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 grows easily from seed and transplants without complaint. Direct sow in early spring as soon as the soil can be worked, and sow again in mid- to late summer for a fall crop, or start seed indoors 6 to 8 weeks before the last frost. Set the seed 1/4 to 3/4 inch deep and space plants 12 to 18 inches apart. Seedlings come up 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 one of the toughest vegetables in the garden, shrugging off frost and light freezes that flatten tender crops. The flavor actually sweetens after a frost as the plant converts starches to sugar. Fall and winter are when kale tastes its best.
You have to pull the whole kale plant to harvest it.
Pick the large lower leaves and leave the central growing point alone, and the plant keeps pushing out fresh leaves. One plant can feed you for weeks or months of repeat harvest instead of a single cutting.