Vegetable · Brassicaceae
Collard Greens
Brassica oleracea (Viridis Group)
An easy, cold-hardy green that keeps handing you leaves long after frost has shut down the rest of the garden.
Full sun
Every 3–7 days
60–80 days
USDA 2–11
Overview
Collards are a leafy cousin in the cabbage family, grown for those broad, blue-green leaves you pick a few at a time instead of for any kind of head. They've been a fixture of Southern gardens and kitchens for generations, but they do just as well way up north. And of all the brassicas, none takes late-fall cold the way a collard can.
What really makes them likeable is how forgiving they are. They're happy in full sun or a touch of shade, they put up with clay, loam, or sandy ground once it's amended, and all they ask for is steady moisture and a bit of nitrogen now and then. Keep picking the lower leaves as they size up and the plant just keeps pushing fresh growth from the center for months.
The best part shows up when it gets cold. A frost won't knock a mature collard back at all. Instead it sweetens the leaves and brings out their best flavor, which is exactly why so many gardeners keep harvesting well into winter, long after the tender crops have called it quits.
Care
The short version: give them full sun, though a little shade is fine, in rich, well-drained soil that stays evenly moist at roughly an inch of water a week. Feed nitrogen as they grow, set plants about 18 inches apart, and pick the lower leaves once they're big enough to use.
Light
Collards do their best work in full sun, but they'll take partial shade too, and a bit of shade actually suits a leaf crop in hot climates. The more sun they get, the quicker and fuller the leaves fill in, so give them an open spot whenever you can.
Water
Keep the soil evenly moist, which works out to about an inch of water a week, soaking the ground at least 6 inches down. Water early in the day so the leaves dry off before night and disease can't get a foothold. Sandy soil drains in a hurry and needs watering more often, and even moisture matters most while young plants are settling in and again as the crop is filling out.
Soil
Go with loamy, well-drained soil that's rich in organic matter, though collards will get by in clay or sand once you've mixed in some compost. Shoot for a pH somewhere between 6.0 and 7.5, leaning neutral, which also helps keep clubroot in check.
Temperature
This is a cool-season crop, and it's comfortable across a pretty wide range, from about 23°F to 86°F (-5°C to 30°C). Mature plants take frost and even light freezes without missing a beat, and it's the cold that does the sweetening.
Humidity
Plain old outdoor humidity is all they want, so there's no number to chase here. What matters more is air movement, because crowded, damp leaves are what invite leaf disease, and that's exactly why spacing them out and watering at the base earns its keep.
Feeding
Mix a preplant fertilizer into the soil based on what a soil test tells you, then side-dress with nitrogen like calcium nitrate about 3 to 4 weeks after planting, and again once more after that. Steady feeding keeps the leaves coming, but don't go overboard, since soft, lush growth is just what aphids are looking for.
Pruning
There's really no pruning to bother with. Crop the lower leaves once they're big enough to use and the plant keeps making new growth from the center, or cut the whole plant at maturity. Snap off any yellowed or diseased lower leaves the moment you notice them.
Size & spacing
Plants get 2 to 4 feet (60 to 120 cm) tall and spread 12 to 24 inches (30 to 60 cm) wide. Leave roughly 18 inches between mature plants so air can move through and leaf disease has less to feed on.
When to plant
Collards are all about cool weather, and you get two seasons out of them. Sow for a spring crop the moment the ground can be worked, then sow again in midsummer for leaves that carry you through fall and into early winter. That fall batch is the one to wait for, because frost only makes it taste better.
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 of what goes wrong with collards is either caterpillars chewing the leaves or trouble down in the roots and soil. Want to stay ahead of it? Flip a few leaves over each week and notice how the plant is holding itself up. Find your symptom below, then act while it can still make a difference.
Yellow V-shaped patches creeping in from the leaf edge
Those yellow triangles with blackened veins are pointing to black rot, a bacterial disease that can't be cured once it takes hold. Pull and destroy the infected plants along with any debris, and stay out of the bed while the leaves are wet so you don't carry it around. Next time, start clean 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 damp but the plant still wilts and stalls out, dig one up and take a look at the roots for swollen, club-shaped galls. That's clubroot, and those damaged roots simply can't draw up enough water. Remove and destroy the whole plant, roots and all, and never toss it on the compost. Keep brassicas out of that bed for at least four years and hold the soil pH near neutral, since the disease hangs on 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 little green droppings
Three pests leave this calling card, and they're all green caterpillars: imported cabbageworms, cabbage loopers, and diamondback moth larvae. Pick off the ones you can see by hand, then spray Bacillus thuringiensis on the leaves to mop up the rest. The most reliable fix? Lay a floating row cover at planting, before the white butterflies and little gray moths ever land to lay their 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 gather on leaf undersides and tuck into the folds of new growth, sucking sap and leaving the foliage twisted and tacky. Knock them off with a hard jet of water, then follow up with insecticidal soap, taking care to coat the undersides where they hide. And go light on the nitrogen, because soft, fast growth is exactly what pulls 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 rushing to flower instead of making leaves. It usually kicks off when young plants sit through a long cold spell and then run into warm weather, or simply because an overwintered plant has hit its second year. Once that stalk goes up there's no taking it back, so harvest whatever leaves are still good and resow. For spring crops, lean on 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 about them, and the ASPCA doesn't flag the plant as a poisoning risk for pets. So you can grow them in a garden full of kids, dogs, cats, and backyard animals and not give it a second thought. The one small footnote is the goitrogens that all brassicas carry, and those only come into play in very large raw amounts, plus they break down once you cook the leaves.
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 perfectly fine, though a big helping of any leafy green can leave the stomach a little loose for a day.
Dogs Safe
There's no toxin here for dogs. Plain, cooked collards even show up in some homemade dog meals. The only thing worth watching is a bit of gas or a soft stool if a dog gulps down a large raw pile.
Horses Safe
Horses can eat collards without any harm. As with other brassicas, just keep it to modest amounts so the cabbage-family greens don't leave a horse gassy and uncomfortable.
Rabbits Safe
Rabbits do great on collard leaves, and they're a common staple in a rabbit's mix of fresh greens. Bring in any new green slowly, and serve it as part of a variety rather than on its own.
Livestock Safe
Cattle, goats, and sheep graze collards as forage with nothing to worry about. Animals switched suddenly onto a lot of lush brassica can bloat, though, so ease them onto it.
Birds Safe
Chickens and other birds peck away happily at collard leaves, and the greens make a healthy treat. Hang up a leaf or chop it small and let them pick at it through the day.
People Safe
Collards are a kitchen staple, good raw or cooked, and safe for everyone at the table. Like all brassicas they carry mild goitrogens, but those only matter in huge raw quantities and cook right out 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 stretch from old Southern heirlooms to newer hybrids bred to shrug off cold and resist bolting. Here are the ones you're most likely to spot on a seed rack.
Georgia Southern
A heat-tolerant heirloom that's been grown all over the Southern US for ages; it never forms a head and just keeps cranking out big, loose leaves.
Vates
The compact, slow-to-bolt heirloom standard, loved for its smooth, blue-green leaves on a neat little plant.
Morris Heading
An heirloom cabbage collard that gathers its tender leaves into a loose head instead of spreading them wide open.
Champion
An improved Vates type bred for tougher cold hardiness and better bolt resistance.
Blue Max
A high-yielding hybrid that puts out heavily savoyed, blue-green leaves.
Top Bunch
An early, even-growing hybrid made for picking individual leaves over and over 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 come from seed, and honestly it's about as easy as gardening gets, whether you drop them right into the bed or start a few plants indoors first.
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, dropped right into the bed in early spring or in midsummer for a fall crop, or started indoors 6 to 8 weeks before you set the plants out. Sow them about a quarter to half an inch deep, and in cool soil the seedlings pop up within 5 to 10 days, ready to transplant in 4 to 6 weeks. Thin them to roughly 6 inches to start, then pull and eat the young plants as they crowd until there's about 18 inches between the ones you're keeping.
Myths
Collards only grow in the South and won't make it through a northern garden.
Collards handle late-fall cold better than anything else in the cabbage family. Gardeners in Illinois and Minnesota grow them just fine, picking leaves well after the first frosts have shut down the rest of the garden.
Frost ruins collard greens.
It's actually the opposite. Mature plants shrug off frosts and even light to medium freezes, and a cold snap really does sweeten the leaves and improve their flavor.