Vegetable · Brassicaceae
Collard Greens
Brassica oleracea (Viridis Group)
An easy, cold-hardy green that keeps giving leaves long after frost has closed down the rest of the garden.
Full sun
Every 3–7 days
60–80 days
USDA 2–11
Overview
Collards are a leafy member of the cabbage family, grown for the broad blue-green leaves you crop a few at a time rather than for any head. They've been a fixture of Southern gardens and kitchens for generations, but they grow just as well far to the north. Of all the brassicas, none takes late-fall cold like a collard does.
What sets them apart is how forgiving they are. They handle full sun or a bit of shade, put up with clay, loam, or sandy ground once it's amended, and ask only for steady moisture and a little nitrogen along the way. Pick the lower leaves as they size up and the plant keeps pushing fresh growth from the center for months.
The real payoff comes in cold weather. A frost doesn't set a mature collard back; it sweetens the leaves and brings out their best flavor. That's why so many gardeners keep harvesting them well into winter, long after the tender crops have given up.
Care
The short version: full sun, with light shade tolerated, in rich well-drained soil kept evenly moist at about an inch of water a week. Feed with nitrogen as the plants grow, space them around 18 inches apart, and harvest the lower leaves as they reach size.
Light
Collards crop best in full sun but will take partial shade, which actually suits a leaf crop in hot climates. The more sun they get, the faster and fuller the leaves come in, so give them an open spot where you can.
Water
Keep the soil evenly moist, about an inch of water a week wetting the ground at least 6 inches down. Water early in the day so the leaves dry before nightfall and disease can't get a hold. Sandy soil drains fast and needs watering more often, and even moisture matters most while young plants settle in and as the crop fills out.
Soil
Plant in loamy, well-drained soil that's rich in organic matter, though collards will manage in clay or sand once you work in some compost. Aim for a pH between 6.0 and 7.5, on the neutral side, which also helps hold clubroot at bay.
Temperature
This is a cool-season crop, comfortable across a wide range from about 23°F to 86°F (-5°C to 30°C). Mature plants take frost and even light freezes in stride, and the cold is what sweetens the leaves.
Humidity
Ordinary outdoor humidity is all they need, so there's no number to hit. Air movement counts for more, since crowded, damp foliage is what invites leaf disease, which is why spacing and base watering pay off.
Feeding
Work a preplant fertilizer into the soil based on a soil test, then side-dress with nitrogen such as calcium nitrate about 3 to 4 weeks after planting, and once more after that. Steady feeding keeps the leaves coming, but don't overdo it, since soft, lush growth is what draws aphids.
Pruning
There's no real pruning to do. Crop the lower leaves once they reach a usable size and the plant keeps making new growth from the center, or cut the whole plant at maturity. Pull off any yellowed or diseased lower leaves as soon as you spot them.
Size & spacing
Plants reach 2 to 4 feet (60 to 120 cm) tall and spread 12 to 24 inches (30 to 60 cm) across. Leave about 18 inches between mature plants so air moves freely and leaf disease has less to work with.
When to plant
Collards run on cool weather and grow in two seasons. Sow for a spring crop as soon as the ground can be worked, then sow again in midsummer for leaves through fall and into early winter. The fall planting is the one most gardeners look forward to, since frost only makes the harvest sweeter.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6-8 weeks before the spring transplant date; sow indoors again in early summer (June) for a fall crop
- Plant: early spring as soon as soil can be worked for a spring crop; mid- to late summer for a fall and early-winter crop
- Harvest: harvest leaves 60-80 days from seeding; flavor sweetens after light fall frosts, and mature plants withstand frosts and light to medium freezes
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most collard problems are caterpillars on the leaves or trouble in the roots and soil. Catch them early by turning a few leaves over each week and watching how the plant carries itself. Match what you see below, then step in while it still does some good.
Yellow V-shaped patches creeping in from the leaf edge
Those yellow triangles with blackened veins point to black rot, a bacterial disease with no cure once it sets in. Pull and destroy infected plants and any debris, and stay out of the bed while the leaves are wet so you don't spread it. Start clean next time with certified disease-free seed, water at the base early in the day, and rotate out of brassicas for several years.
Fix:
- Remove and destroy infected plants and debris
- Avoid working among wet plants
- There is no cure once infection is established
Plants wilting in warm sun even though the soil is wet
When the soil is moist but the plant still wilts and stalls, dig one up and check the roots for swollen, club-shaped galls. That's clubroot, and the damaged roots simply can't pull up enough water. Remove and destroy the whole plant, roots and all, and never compost it. Keep brassicas out of that bed for at least four years and hold the soil pH near neutral, since the disease lingers in acidic ground.
Fix:
- Remove and destroy infected plants including roots
- Do not compost infected material
- Do not replant brassicas in the affected bed
Ragged holes in the leaves with green droppings
Three pests do this damage, all of them green caterpillars: imported cabbageworms, cabbage loopers, and diamondback moth larvae. Pick them off by hand and spray Bacillus thuringiensis on the leaves to clear the rest. The surest fix is a floating row cover laid down at planting, before the white butterflies and small gray moths ever land to lay eggs.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt) to foliage
- Cover plants with floating row cover at planting to exclude egg-laying adults
Curled, puckered leaves with a sticky film
Aphids cluster on the undersides of leaves and in the folds of new growth, sucking sap and leaving the foliage twisted and tacky. Blast them off with a hard jet of water, then treat with insecticidal soap, making sure to coat the leaf undersides where they hide. Go easy on the nitrogen, since soft, fast growth is exactly what draws them in.
Fix:
- Dislodge with a strong stream of water
- Apply insecticidal soap, thoroughly covering leaf undersides
- Remove heavily infested leaves
A flower stalk shoots up and the leaves turn bitter
This is bolting, the plant racing to flower instead of making leaves. It happens when young plants sit through a long cold spell and then hit warm weather, or simply because an overwintered plant has reached its second year. There's no reversing it once the stalk goes up, so harvest whatever leaves are still good and resow. For spring crops, pick bolting-tolerant cultivars and don't rush transplants out into lingering cold.
Fix:
- Harvest remaining usable leaves promptly
- Remove the plant and resow for the next season
Toxicity
Collards are a safe, edible green with nothing toxic in them, and the ASPCA doesn't list the plant as a poisoning risk to pets. You can grow them in a garden shared by children, dogs, cats, and backyard animals without worry. The only mild note is the goitrogens common to all brassicas, which matter only in very large raw amounts and break down in cooking.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
Collards aren't toxic to cats, and the ASPCA doesn't list them as a poisoning risk. A cat that nibbles a leaf is fine, though a big helping of any leafy green can loosen the stomach for a day.
Dogs Safe
No toxin here for dogs. Cooked, plain collards even turn up in some homemade dog meals. The only thing to watch is gas or a soft stool if a dog wolfs down a large raw pile.
Horses Safe
Horses can eat collards without harm. As with other brassicas, keep it to modest amounts so the cabbage-family greens don't leave a gassy horse uncomfortable.
Rabbits Safe
Rabbits do well on collard leaves, and they're a common staple in a rabbit's mix of fresh greens. Introduce any new green slowly and serve it alongside variety rather than on its own.
Livestock Safe
Cattle, goats, and sheep graze collards as forage with no poisoning concern. Animals shifted suddenly onto large amounts of lush brassica can bloat, so ease them onto it.
Birds Safe
Chickens and other birds peck happily at collard leaves, and the greens make a healthy treat. Hang a leaf or chop it small and let them work at it through the day.
People Safe
Collards are a kitchen staple, good raw or cooked, and safe for everyone in the family. Like all brassicas they carry mild goitrogens, which only matter in huge raw quantities and cook away in the pot.
No special handling precautions. Like other brassicas, collards contain goitrogenic compounds, a minor dietary note at very high raw intake rather than a poisoning risk.
Varieties
Collard varieties run from old Southern heirlooms to modern hybrids bred for cold and bolt resistance. These are the ones you'll see most often on a seed rack.
Georgia Southern
A heat-tolerant heirloom long grown across the Southern US that never forms a head and just keeps making big loose leaves.
Vates
The compact, slow-to-bolt heirloom standard, prized for its smooth blue-green leaves on a tidy plant.
Morris Heading
An heirloom cabbage collard that gathers its tender leaves into a loose head rather than spreading them open.
Champion
An improved Vates type bred for stronger cold hardiness and better resistance to bolting.
Blue Max
A high-yielding hybrid carrying heavily savoyed, blue-green leaves.
Top Bunch
An early, uniform hybrid built for repeated cropping of individual leaves through the season.
Companions
Collards do best kept well away from their cabbage-family relatives, which trade the same pests and soil diseases back and forth.
Keep apart
other brassicas (cabbage, broccoli, kale, Brussels sprouts): They share the same pests and soilborne diseases such as clubroot; extension guidance is to avoid planting collards where any brassica-family crop has grown within the past four years
How to propagate
Collards are grown from seed, and it's about as simple as gardening gets, whether you sow straight into the bed or start a few plants indoors.
SeedEasy
Direct sow in early spring or in midsummer for a fall crop; or start indoors 6-8 weeks before transplanting · Germinates in about 5-10 days in cool soil; transplant-ready in 4-6 weeks
Collards grow easily from seed, sown straight into the bed in early spring or in midsummer for a fall crop, or started indoors 6 to 8 weeks before you set plants out. Sow about a quarter to half an inch deep, and in cool soil the seedlings come up within 5 to 10 days, ready to transplant in 4 to 6 weeks. Thin them to roughly 6 inches at first, then pull and eat the young plants as they crowd until about 18 inches stands between the ones you keep.
Myths
Collards only grow in the South and won't survive a northern garden.
Collards take more late-fall cold than any other plant in the cabbage family. Gardeners in Illinois and Minnesota grow them well, picking leaves long after the first frosts have shut down the rest of the garden.
Frost ruins collard greens.
It's the other way around. Mature plants shrug off frosts and even light to medium freezes, and a cold snap actually sweetens the leaves and improves their flavor.