How to Grow Collard Greens

A green for both ends of the season

Collards belong to the same species as cabbage and kale, but they cope with heat better than either kale or turnip greens. Maryland Extension notes the trade-off: they are a little less cold-tolerant. Clemson Extension says collards will grow in South Carolina most of the year, although spring and fall plantings give the best results. UF/IFAS describes them as both cold- and heat-tolerant, and adds that cool-season greens taste better.

Cold tolerance depends on whom you ask. Clemson says mature plants survive frosts and light to medium freezes. Maryland classes collards as hardy, able to take heavy spring and fall frosts. Nebraska Extension puts them among the semi-hardy crops that tolerate only light frost, around 30 to 32°F. In cold-winter areas, treat collards as a crop to finish or cover before hard freezes.

When to plant

In spring, Maryland Extension sows seed as soon as the soil can be worked, about 3 to 4 weeks before the last frost, or sets out young transplants at that time. Clemson prefers transplants for spring because seed germinates slowly in cool soil. The two disagree on transplant age: Maryland uses 3- to 5-week-old plants, while Clemson starts them indoors 6 to 8 weeks ahead.

Spring plantings bring a bolting risk. A cold spell after a period of good growth can make any collard flower, so Clemson recommends a bolt-tolerant variety for spring.

For fall, late-summer direct seeding works well because the soil is warm. Maryland’s rule is to take the variety’s days to maturity, add 10 to 14 days for slower growth in shortening days, and sow that many days before the first frost. With collards taking 60 to 80 days from seed, that means sowing roughly 10 to 13 weeks ahead. Purdue, working with an 80-day collard, sets an earlier last planting date for collards than for kale. The dates for your zone above apply this timing.

In frost-rare areas, plant from late summer through winter. North Florida also gets a late-winter-to-spring window, according to UF/IFAS, and Texas A&M times collards like broccoli in the Lower Rio Grande Valley.

Planting and spacing

Sow seed ¼ to ½ inch deep. Clemson warns that seed buried deeper than ½ inch often fails to come up. Keep the soil moist while seedlings establish and thin them at the three-leaf stage. In hot late-summer soil, Purdue suggests a light layer of compost, vermiculite or potting soil over the seed row to prevent crusting, and Nebraska shades the row with a board or light mulch to keep the soil cooler.

Spacing advice ranges widely. Clemson uses 6 to 18 inches between plants in rows 18 to 36 inches apart. UF/IFAS and Maryland both give 12 to 24 inches, and Texas A&M’s Rio Grande Valley guide 18 inches. Wide spacing produces big plants for a long picking season; Maryland notes that plants only 2 to 4 inches apart give a crop of small leaves you can cut repeatedly.

Soil, feeding and water

Collards need full sun but will produce in partial shade with 4 to 6 hours of direct light, according to Maryland Extension. Keep the soil pH at 6.0 to 6.5 and fertilize before planting according to a soil test.

Collards respond strongly to nitrogen, which is what keeps new leaves coming. Clemson side-dresses with calcium nitrate (15.5-0-0) 3 to 4 weeks after planting and again 3 to 4 weeks later, at about ½ pound per 100 square feet or 30 feet of row. Keep the fertilizer 4 to 6 inches from the stems. If you broadcast it, water overhead afterward so granules do not burn the leaves.

Water enough to wet the top 6 inches evenly. Do it early in the day so the leaves dry before night, which reduces leaf disease. Clemson singles out two stages when steady moisture matters most: while seedlings establish and as the crop matures. Wilting leaves mean the soil is too dry. Mulch helps on both counts.

Varieties for the South

• South Carolina: Clemson lists the hybrids Blue Max, Flash, Top Bunch 2.0, Tiger and Champion, and the heirlooms Georgia Southern, Morris Heading and Vates. Georgia Southern dates from the 1880s.
• Florida: Georgia, Georgia Southern, Top Bunch and Vates (UF/IFAS).
• Lower Rio Grande Valley, Texas: Champion, Vates, Flash and Georgia Southern (Texas A&M).

Pests and diseases

• Caterpillars. Imported cabbageworms, cabbage loopers and diamondback moth larvae are the main leaf chewers. Hand-pick them or spray Bt.
• Harlequin bugs and aphids. Harlequin bugs feed on collards, and aphids tend to show up in fall. Check plants often and remove them early.
• Black rot. This is a bacterial disease. Start with clean seed and rotate cabbage-family crops.
• Downy mildew and Alternaria leaf spot. Both are favored by wet leaves, so water early in the day.
• Fusarium yellows. Clemson flags this disease on summer-grown collards.

Harvest and storage

Leaves are ready about 2 months after planting; Clemson gives 60 to 80 days from direct seeding, and UF/IFAS gives 50 to 70 days from transplants. Pick the lower leaves while they are full-sized, deep green and tender, before they yellow or toughen. Take only a few from each plant, working up the stem, so it has time to recover. UF/IFAS advises never removing more than a third of the plant at one time. You can also cut whole plants when they are half or fully grown.

Refrigerate leaves in a plastic bag for up to about 2 weeks.