Collard Greens

Direct sow as soon as the soil is workable

Sow seed a quarter to a half inch deep in rows 18 to 30 inches apart as soon as the soil can be worked in spring. Once the seedlings are up, thin them to stand 8 to 12 inches apart, or as close as 4 inches if you only want baby leaves. Collards are a cool-season brassica that builds its best leaves in cool weather, so a spring sowing needs the whole cool window ahead of it before summer heat turns the leaves tough and bitter.

Sow the fall crop about three months before your first frost

Count back roughly three months from your average first fall frost and direct sow then, or start transplants indoors in midsummer to set out in late summer. Do not wait for cool weather to arrive - the plants need to reach size while it is still warm. The fall crop is the better crop: the plants size up in late summer and then sweeten as the weather cools, and they keep producing well beyond the first frosts rather than bolting the way a spring crop does when heat arrives.

Use transplants for the spring crop, started 6 to 8 weeks ahead

Start seed indoors 6 to 8 weeks before you intend to set plants out, and transplant into rows 18 to 36 inches apart with plants 6 to 18 inches apart in the row - the wider spacing if you want full-sized plants, the tighter if you will cut them half-grown. Transplants are the preferred planting material for a spring crop because seed germinates slowly in cool spring soil, and a head start is what lets the crop finish before heat forces it to bolt.

Give an inch of water a week and never let growth stall

Aim for about one inch of rainfall or irrigation per week. Check with a trowel rather than by eye, and water more often on sandy soils, which dry from the top down faster than the leaves show. Leaf quality comes from fast, unchecked growth - a plant stalled by heat or drought stress makes tough, strong-flavored leaves, and no amount of later watering makes them tender again.

Side-dress nitrogen three to four weeks after planting, then again

Three to four weeks after planting, side-dress with calcium nitrate (15.5-0-0) at about 5 pounds per 1,000 square feet, placing it 4 to 6 inches away from the plants, and repeat once more. Do the same for a fall planting. Keep soil pH between 6.0 and 6.5. Collards are grown for leaves alone, so nitrogen is the yield - it drives the deep green color and the tender growth, and a plant that runs short of it makes small, pale, leathery leaves.

⚠ Keep side-dressed fertilizer 4 to 6 inches off the plants - banding it against the stems burns the roots.

Scout leaf undersides weekly for caterpillars before you spray

Once a week, check the undersides of leaves on at least 25 plants chosen at random, looking for larvae, frass and feeding holes, and note which species you have. Collards are a leafy green, so treat when 10 percent of plants are infested; cross-striped cabbageworm warrants treatment at 5 percent because it feeds in groups. Better still, lay fine-mesh row cover immediately after planting and bury the edges - but skip row cover on unrotated ground, where the pests overwinter underneath it. Imported cabbageworm, cabbage looper and diamondback moth all feed on the undersides of leaves where you will not see them from above, and on a leaf crop the damage is the harvest - a threshold catches them while the larvae are still small enough for Bt to kill.

Black rot: pull infected plants and stay out of wet foliage

Watch for yellow V-shaped lesions running in from the leaf margins with blackened veins, especially in warm wet spells around 80 to 86 F. Remove infected plants immediately, avoid overhead irrigation, do not handle or harvest plants while the leaves are wet, and rotate to a non-host for at least three years. Start with certified disease-free seed. Black rot is a seed-borne bacterium that enters through the hydathodes at the leaf margins and then plugs the water-conducting vessels, and splashing water or wet hands move it plant to plant faster than the symptoms appear.

Caterpillars: spray Bt while the larvae are still small

When scouting hits the threshold, spray Bacillus thuringiensis, covering the undersides of the leaves thoroughly. Use the aizawai strain rather than kurstaki where diamondback moth is the problem, as it holds up better against resistant populations. Spinosad is the stronger alternative if Bt is not holding. Only treat active larvae - pupae and adults do no further damage. Bt has to be eaten to work and it kills young caterpillars far more reliably than large ones, so the spray is only worth making while the larvae are small and still feeding on the leaf surface you can reach.

⚠ Bt carries a 0-day harvest interval and spinosad a 1-day interval on cole crops - check your own label. Spinosad is toxic to bees until the spray dries, so never spray a plant that has bolted into flower, and rotate materials to slow resistance in diamondback moth.

Pick outer leaves from the bottom up and let frost sweeten them

Start harvesting around 60 to 80 days when the outer leaves reach 8 to 10 inches, taking no more than a third of the lower leaves at a time and working from the bottom up so the growing point keeps producing. Alternatively cut whole plants half-grown or full-grown. Keep picking through the first frosts and freezes. Cold converts the plant's stored starches to sugars, so the leaves taken after a frost are genuinely sweeter than the same leaves in September - and stripping only the bottom third leaves the crown enough leaf area to rebuild the next picking.