Vegetable · Brassicaceae
Kale
Brassica oleracea Acephala Group
Easygoing and giving, kale hands you tender leaves from spring right through winter.
Full sun
Every 3–7 days
55–75 days
USDA 2–11
Overview
Kale is a leafy cousin of cabbage, but instead of balling up into a head it stays open in a loose rosette you can pick from as it grows. It shows up in all sorts of looks, from the ruffled blue-green curls of the common types to the long, puckered straps of the Italian heirlooms. And the best news for anyone just starting out? It's about as easy as vegetables get.
At heart it's a cool-season crop, so it does its best work in the mild stretches of spring and fall, and it shrugs off frost that would knock out a tomato overnight. Funny thing is, the cold actually helps, because a hard chill turns the leaves sweeter and milder instead of tougher.
Give it full sun, steady water, and rich soil, and a single planting just keeps feeding you for months. You pick the outer leaves whenever you want them and leave the center to carry on, so the harvest spreads out rather than arriving all at once.
Care
The short version: kale likes full sun and rich, evenly moist soil with roughly an inch to an inch and a half of water a week. Feed it as the season rolls on, plant it once for spring and again for fall, and just pick the lower leaves whenever you need some.
Light
Kale really wants full sun, at least 6 hours a day, if you want it full and leafy. It'll cope with partial shade too, which comes in handy where the summers get hot, but deep shade just leaves you with thin, slow plants and not many leaves.
Water
Keep the soil evenly moist with about 1 to 1.5 inches of water a week. That steady moisture is what keeps the leaves tender and mild instead of tough and bitter, so a layer of mulch to lock the water in is well worth it.
Soil
Give kale fertile, well-drained loam worked over with plenty of organic matter. A pH of 6.0 to 7.5 suits it, and if your soil runs acidic, nudging it toward the top of that range does double duty by helping keep clubroot at bay.
Temperature
This is a cool-season crop that's happy anywhere from 10°F to 81°F (-12°C to 27°C). It takes hard frost in stride, and the cold even sweetens the leaves, but real summer heat is what turns them bitter and sends the plant rushing to bolt.
Humidity
Kale doesn't fuss over humidity, so there's no number you have to hit. What matters way more is good airflow, because crowded, damp leaves are exactly what invite the aphids and diseases that bother brassicas.
Feeding
Work a balanced fertilizer into the bed at planting, guided by a soil test, then side-dress with a bit of nitrogen about 4 to 6 weeks on to keep the leaves coming. Don't go overboard with the nitrogen though, or the soft, lush growth just brings in aphids.
Pruning
Kale doesn't really need pruning. Harvest the lower, outer leaves once they're big but still tender, leave the central growing point alone so the plant keeps producing, and just snap off any leaf that yellows or gets chewed.
Size & spacing
Plants get to about 1 to 3 feet (30 to 100 cm) tall and spread nearly as wide, so give them elbow room. Set them 12 to 18 inches (30 to 45 cm) apart so air can move between them and each one has space to fill out.
When to plant
Kale is all about cool weather and a nice long run. Sow it in early spring for an early summer cutting, then sow it again in midsummer for a fall and winter crop that only gets sweeter once the cold moves 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 of kale's troubles turn up on the leaves, right where the chewing pests and sap-suckers do their thing out in the open. Peek under the leaves often and you'll catch things early. Find your symptom below, then jump on it before it spreads.
Plants wilting and stunted with swollen, distorted roots
If a plant keeps wilting in the afternoon, yellows, and just won't grow, dig it up and have a look at the roots. Thick, club-shaped lumps mean clubroot, a soilborne disease that can't be cured once it's in the ground, while tunneled roots with little white grubs point to cabbage root maggot instead. Pull and destroy anything infected rather than composting it, then move your brassicas to fresh soil 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
See ragged holes with green droppings scattered below? That's cabbageworms and cabbage loopers, usually with a few diamondback moth larvae mixed in. Pick the caterpillars off by hand, and if they keep coming, reach for Bt or spinosad. The tidy long-term fix is a floating row cover laid over the plants at transplanting, which keeps the moths from laying eggs at all.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) or spinosad according to label directions
Curled, sticky leaves with clusters of small insects
Those waxy gray-green clumps hiding in the leaf folds are cabbage aphids, and they're simpler to deal with than they look. Hit them with a hard jet of water, then follow up with insecticidal soap and don't forget the undersides, since that's where they lurk. Wondering about the lady beetles and parasitic wasps you spot nearby? Leave them be, because they'll handle the next round for you.
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
Those little round pits are the calling card of flea beetles, shiny black specks that ping away the second you go to grab one. They mostly pester seedlings in warm, dry spring weather and hardly ever knock a strong plant off course. So keep the young ones under row cover and growing fast, and they'll simply outpace the nibbling.
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, so it's safe for you and for the animals hanging around the garden. There's no toxin to stress about, and the only real footnote is moderation: heaps 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
No need to panic if the cat sneaks a nibble, because kale isn't toxic to them at all. If one really goes to town on a pile of raw leaves, you might see a bit of gas or a soft stool, and that's about it.
Dogs None
Plain kale is fine for dogs, and you'll spot it in lots of homemade dog dinners. Just keep servings small, since a big sudden helping of the raw leaves can leave a dog gassy or a little off.
Horses Safe
Kale won't poison a horse, so a taste now and then is no problem. Think of it as an occasional treat rather than a daily ration, because a steady stream of brassica greens can act as a mild goitrogen over time.
Rabbits Safe
Rabbits can have kale as one green among several in the mix. Ease it in slowly and keep the helpings small so it doesn't push out the hay their tummies really need.
Livestock Safe
Cattle, goats, and sheep graze kale just fine, and it's even grown on purpose as a forage crop. Pile on the foliage every single day, though, and it can act as a goitrogen, so mix it with other feed.
Birds Safe
Chickens and other birds love a good peck at kale, leaves, stalk, and all. It's a healthy green treat, and there's nothing toxic in it to steer them around.
People Safe
For people, kale is an everyday vegetable that's great raw in a salad or cooked up. Give it a quick rinse first, just like you would any leafy green fresh 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
There are dozens of kale cultivars out there, but only a handful keep popping up in gardens and on extension lists. These are the ones really worth knowing by name.
Lacinato (Tuscan, Dinosaur)
It's an Italian heirloom with narrow, dark blue-green, heavily puckered strap-like leaves, and it's a type UF/IFAS points to for Florida gardens.
Winterbor
Winterbor is a really cold-hardy hybrid that grows tall and keeps cranking out finely curled blue-green leaves.
Redbor
Redbor is a deep red-purple curly hybrid that looks good enough for the flower bed, and its color only gets richer once the weather cools.
Red Russian
Red Russian is one of the sweetest kinds you can grow, with tender, flat, toothed gray-green leaves and purple veins and stems.
Vates Dwarf Blue Curled
Vates Dwarf Blue Curled is a compact, low-growing curly standard that shrugs off bolting and has been an extension favorite forever.
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 easiest vegetables to get going, since it sprouts happily from seed sown right 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 from seed without any fuss, whether you sow it right in the ground or raise it as transplants. Sow the first batch in early spring the moment the soil's workable, sow again in mid- to late summer for a fall crop, or get going indoors 6 to 8 weeks before the last frost. Pop the seed in 1/4 to 3/4 inch deep and give plants 12 to 18 inches of space. You'll see seedlings in about 5 to 10 days, they're ready to set out in 4 to 6 weeks, and they mature in roughly 55 to 75 days.
Myths
Frost ruins kale, so you have to finish the crop before the cold shows up.
Actually, kale is one of the toughest vegetables you can grow, and it shrugs off frost and light freezes that flatten tender crops. Here's the fun part: the flavor sweetens after a frost, because the plant turns its starches into sugar. Fall and winter are when kale tastes its best.
You've got to pull the whole kale plant to harvest it.
Nope, just pick the big lower leaves and leave the central growing point alone, and the plant keeps sending up fresh ones. So one plant can feed you for weeks or months of picking, not just a single cutting.