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How to Grow Collard Greens: Sowing to Harvest

Collards tolerate more heat and more cold than any other brassica, and frost genuinely sweetens them. Sow, space wide, and pick from the bottom up.

By Zakaria 3 min read Save to Pinterest — opens Pinterest in a new tab
Collard greens leaves
Photo: GregReese, Pixabay Content License, via Pixabay
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Collards are the most forgiving brassica there is — they take more heat and more cold than kale, cabbage or broccoli — and the only two things people reliably get wrong are spacing and when to sow.

Two sowing windows, and one is better

When to sow, and what you get
SowingHarvestFlavour
Late summer (6–8 wks before first frost)Autumn into winterSweet — frost-improved
Early spring (6–8 wks before last frost)Early summerHarsher; bolts in heat

The autumn crop is the one to plan around. Collards mature into falling temperatures, and cold converts stored starch into sugars — a genuine physiological change that acts as antifreeze in the leaf and tastes markedly sweeter.

The spring crop works, but it runs into summer heat, which drives up the bitter glucosinolates and eventually causes bolting.

In mild regions collards are simply a winter standing crop, picked as needed from October through March.

Spacing: the mistake almost everyone makes

Eighteen to twenty-four inches. Not twelve, not eight.

A mature collard is a big plant — leaves a foot or more across on a stem that can reach three feet. Crowding costs you three ways:

  1. Small leaves, from competition for water and nutrients
  2. Disease, because still humid air between crowded plants is what downy mildew and black rot need
  3. Harder picking, since you cannot get at the lower leaves

If you direct-sowed thickly, thin hard and eat the thinnings — they are excellent.

Mesh before pests, not after

Cabbage whites, loopers, aphids, flea beetles and harlequin bugs all target brassicas, and by the time you see damage the population is established.

Fine insect mesh over hoops, fitted at planting, excludes essentially all of them and removes the need to spray anything. It is the single highest-return thing you can do for a brassica bed.

Check leaf undersides weekly anyway — that is where aphid colonies and caterpillar eggs sit.

Picking so the plant keeps going

This is what makes collards worth the space. They grow from a single central growing point that keeps producing new leaves, so the plant is not a one-time harvest.

  • Take the outer, lower leaves, starting when they are around ten inches
  • Never cut the central bud. That ends production permanently
  • No more than a third at once, so the plant keeps enough foliage to fuel itself

Done this way, a handful of plants produces for months — and in a mild winter, straight through to spring.

If they taste bitter

Three causes, in order of likelihood:

Heat. Collards grown through hot weather produce more bitter compounds. Time the crop for cool conditions.

Inconsistent water. They are shallow rooted, so drying out and re-soaking toughens the leaves. An inch to an inch and a half a week, plus mulch to even out the swings.

Age. Very large old outer leaves are coarse whatever you do. Pick younger.

Feeding

Collards are grown entirely for leaf, so nitrogen is the nutrient that matters. Work plenty of compost in before planting and give a nitrogen-rich feed about four weeks after.

A hungry collard makes small, tough, bitter leaves — which is the same complaint as above arriving by a different route.

Step by step

Time
P75D
Cost
15
You need
Collard seed or transplants, Compost or well-rotted manure, Mulch
Tools
Insect mesh or row cover, Hand fork

  1. Pick the right sowing window

    Sow in late summer for an autumn and winter crop, which is the better of the two windows, or in early spring six to eight weeks before the last frost for a summer crop. The autumn sowing runs into cold weather, which improves the flavour.

  2. Prepare a sunny bed with rich soil

    Six hours of sun minimum and plenty of compost worked in. Collards are heavy feeders and a hungry plant produces small, tough, bitter leaves.

  3. Sow a quarter inch deep or set out transplants

    Direct sow thinly, or plant transplants at the depth they were growing. Collards transplant well, unlike most root crops, so starting in modules is a reasonable option.

  4. Space plants 18 to 24 inches apart

    This is wider than most people expect and it is the step most often got wrong. A mature collard is a large plant, and crowding produces small leaves and the still, humid air that invites fungal disease.

  5. Cover with insect mesh from day one

    Cabbage white butterflies, loopers and aphids all target brassicas. Fine mesh laid over hoops before the pests arrive is far more effective than treating an infestation later.

  6. Mulch and water consistently

    An inch to an inch and a half of water a week. Collards are shallow rooted and uneven watering is what makes the leaves tough and bitter.

  7. Feed once plants are established

    A nitrogen-rich feed about four weeks after planting keeps leaf production going. Collards are grown entirely for foliage, so nitrogen is the nutrient that matters.

  8. Start picking the lower leaves at about 10 inches

    Take the outer, lower leaves and leave the central growing point untouched. The plant keeps producing from the centre for months, which is why a few plants feed a household.

  9. Take no more than a third at a time

    Leave enough foliage to keep the plant fuelled. Stripping a collard sets it back far longer than the few extra leaves are worth.

  10. Leave them out through frost

    Collards survive hard frost and down to roughly 20 F, and cold converts starch to sugar so the leaves become noticeably sweeter. Harvest right through winter in mild regions.

Common questions

When should you plant collard greens?

There are two windows and the autumn one is better. Sow in late summer, roughly six to eight weeks before your first frost, for a crop that matures into cold weather and tastes sweeter for it. Or sow in early spring, six to eight weeks before the last frost, for a summer crop that will be harsher in flavour and more prone to bolting once real heat arrives. Collards tolerate both ends better than any other brassica, which is why they are grown year-round across much of the southern US.

How far apart should collard greens be spaced?

Eighteen to twenty-four inches apart, which is considerably wider than most people plant them. A mature collard is a large plant with leaves a foot or more across, and crowding gives you small leaves, competition for water and nutrients, and the still humid air in which downy mildew and black rot take hold. If you sowed thickly, thin ruthlessly and eat the thinnings.

Do collard greens taste better after a frost?

Yes, and the effect is real rather than folklore. Cold triggers the plant to convert stored starch into sugars, which act as a natural antifreeze in the leaf tissue, and the result is a noticeably sweeter and less bitter leaf. This is the same mechanism that improves kale, parsnips and brussels sprouts after frost, and it is the main argument for timing the crop to mature in late autumn rather than midsummer.

How do you harvest collards so they keep producing?

Pick the outer, lower leaves and never cut the central growing point. Collards grow from a single apical bud that keeps producing new leaves from the centre, so as long as that is intact the plant carries on for months — a well-managed plant can be picked from for an entire season. Take no more than about a third of the foliage at once, starting when leaves are around ten inches long.

Why are my collard greens bitter and tough?

Usually heat, drought or age. Collards grown through hot weather produce more of the bitter glucosinolates, inconsistent watering toughens the leaves because the plant is shallow rooted and stressed, and very old outer leaves are coarse regardless of conditions. The fixes are to time the crop for cool weather, water consistently to about an inch and a half a week, mulch to even out soil moisture, and pick leaves while they are young rather than letting them become enormous.

What pests attack collard greens?

The brassica regulars: cabbage white caterpillars, cabbage loopers, aphids, flea beetles and harlequin bugs. Fine insect mesh over hoops, put on at planting rather than after damage appears, handles nearly all of them and is far more effective than spraying. Check the undersides of leaves weekly, since both aphid colonies and caterpillar eggs are laid there and are easy to deal with before they establish.

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