Prepared by Powell Smith, Lexington County Extension Agent, and Nancy Doubrava, HGIC Horticulture Specialist, Clemson University. New 06/99. Revised 04/03. Images added 08/15.
Collards (Brassica oleracea, Acephala Group) are cool-season plants that should be grown in early spring or fall. They grow best at temperatures of 60 to 65 °F. Like many other cool-season crops, they will bolt or produce a flower stalk if exposed to a prolonged cold period following a favorable growing period. These crops must be planted early enough in the spring to ensure that the crop is harvested before temperatures become too hot. The mature plant will withstand frosts and light to medium freezes.
Collards that are bolting due to prolonged cold period.
Karen Russ, ©2009 HGIC, Clemson Extension
|Piedmont||---||July 1-Aug. 30|
|Central||Feb. 25-Mar. 20||July 15-Aug.15|
|Coastal||Feb. 20-Mar 15||Aug 1-Aug 25|
Piedmont: Abbeville, Anderson, Cherokee, Chester, Edgefield, Fairfield, Greenville, Greenwood, Lancaster, Laurens, McCormick, Newberry, Oconee, Pickens, Saluda, Spartanburg, Union and York counties.
Central: Aiken, Allendale, Bamberg, Barnwell, Calhoun, Chesterfield, Clarendon, Darlington, Dillon, Florence, Kershaw, Lee, Lexington, Marion, Marlboro, Orangeburg, Richland and Sumter counties.
Coastal: Beaufort, Berkeley, Charleston, Colleton, Dorchester, Georgetown, Hampton, Horry, Jasper and Williamsburg counties.
Transplants can be grown and set out in early spring. It takes about six to eight weeks to produce plants ready for transplanting. Plant collards in rows that are 3 feet apart. Spacing within the row depends on when the crop will be harvested. If plants are to be harvested when half-grown, they may be spaced 10 to 15 inches apart. If they will be harvested when full-grown, space the plants 15 to 18 inches apart.
Direct seeding is possible, especially for the fall crop. Loamy to sandy soil is best for direct seeding. It is critical to keep the soil moist during seedling establishment. It is also desirable to have an area that is protected from the wind when seeding these crops. Plant seed in moist soil about ½ to ¾ of an inch deep but never deeper than an inch.
Direct-seeded plantings should be thinned to the desired stand when the plants are in the three-leaf stage. If young, direct-seeded plants are to be harvested similar to mustard greens, the plants may be spaced 2 to 4 inches apart. Rows should be 3 feet apart.
Champion collard plant.
Karen Russ, ©2009 HGIC, Clemson Extension
Collards may be grown on a variety of soils. Heavier loamy soils will produce the greatest yields. The light, well-drained, sandy soils are best for early spring crops. Soils should be well-drained, rich in organic matter and have a pH of 5.8 to 6.5. Have your garden soil tested several months prior to planting and adjust soil pH according to recommendations.
Leafy vegetables require quick, continuous growth for best quality. They need ample nitrogen for good green color and tender growth. A soil test is always the best method for determining the fertilization needs of the crop. Information on soil testing is available in the fact sheet HGIC 1652, Soil Testing.
If a soil test has not been taken, apply 5-10-10 at 3 pounds per 100 square feet before planting. This crop should be sidedressed once during the growing season. Sidedress with 33-0-0 at 1 pound per hundred feet of row or calcium nitrate at 2 pounds per 100 feet of row. More frequent sidedressing may be required if the garden is sandy or leaching rains occur. Nitrogen is important for these crops to produce a high-quality product.
Collards growing in a home garden.
Barbara H. Smith, ©2015 HGIC, Clemson Extension
Water the garden to provide a uniform moisture supply to the crop. Water the garden in the morning so the leaves will be dry before nightfall. Water sufficiently to moisten the soil to a depth of at least 6 inches. Light sprinklings will encourage shallow rooting of the plants. The critical periods for moisture are stand establishment and crop maturation. It is important to have a constant uniform moisture supply to produce a high-quality crop and to have the spring crop mature before high summer temperatures. Mulching can help conserve water and reduce weeds.
Collards should be ready for harvest 70 days after direct seeding. Entire plants can be cut when very young, half-grown or full-grown. Tender leaves can also be harvested from full-grown plants. Store all harvested collards in the refrigerator.
Several worms (imported cabbageworm, cabbage looper, diamondback moth caterpillar) and harlequin bugs are the major insect problems. Aphids can also be a serious problem, especially during cool weather.
Common disease problems include black rot, downy mildew and Alternaria leaf spot. Fusarium yellows may be a problem on summer-grown collards.
Excerpted from Home Vegetable Gardening, EC 570, 2002.
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