direct seeded leafy greens; photo by Michael Hofferber
“Leafy greens,” or simply “greens,” are broad terms used for a number of vegetable crops with edible leaves. Plants in this group belong to several unrelated taxonomic plant families that include Brassicaceae, Lactuca, Chenopodiaceae, Spinacia, and Asteraceae.
Collards and kale (Brassica oleracea L.) belong to the same group as cauliflower, cabbages, broccoli and kohlrabi but in a subgroup that is called Acephala (non-heading types). They are cold tolerant and leaves are usually cooked before eating.
Lettuce (Lactuca sativa L.) is a plant in the daisy family that can be eaten raw or cooked. Leaf lettuce grows very fast and is very easy to grow in home gardens. This cool-weather crop does very well at temperatures around 63 degrees F and becomes dormant when it is too hot.
seedling Spinacia oleracea L.; photo by Michael Hofferber
Spinach (Spinacia oleracea L.) is a plant in the Amaranth family. The leaves can be smooth or ruffled in texture. It is a cool-season, cold-tolerant vegetable that tends to form flower heads when it is too hot.
Turnip greens (Brassica rapa L.) is a plant in the Chinese cabbage group. Varieties grown for leaves have very small or no storage roots. It is a cool-season vegetable that performs well in cool weather.
Mustard greens (Brassica juncea L.), sometimes referred to as leaf mustard, has a distinct pungent flavor.The leaves and stems are edible, and it is used in Asian and African cuisines, including the preparation of soul foods. This plant is easy to cultivate and grows very fast.
Arugula (Erica sativa Mill) is an annual plant native to the Mediterranean region. It looks like a longer-leaved and open lettuce.
Most leafy greens are direct seeded; kale, collards, lettuce and Swiss chard can be transplanted. Seeds can be started indoors at least four weeks before transplanting. Harden seedlings by exposing them to outdoor environment gradually two to three days before transplanting.
Transplant kale and collards 8 inches apart, leaf and Bibb lettuce 8 to 12 inches apart, head lettuce 10 to 12 inches apart, and Swiss chard 4 to 6 inches apart in rows 18 inches apart.
Direct seed collards, kale, lettuce and spinach as soon as the ground can be worked and at least two to three months before the fall frost date. Plant seeds one-fourth to one-half inch deep in rows that are 18 to 30 inches apart. After plant emergence, thin collards, kale, leaf lettuce, and Bibb lettuce to 8 to 12 inches apart.
Thin Swiss chard 4 to 6 inches apart and spinach 2 to 4 inches apart. Spinach can be planted every one to two weeks until outdoor temperatures reaches 80 degrees F for continuous harvest during the growing season.
Plant leafy greens in a location with full sun; fertile, well-drained soil; and near a water source. Control weeds by hand pulling or cultivation, but do not dig deep close to the base of the plants to avoid root injury. Leafy greens can also be mulched with a 3- to 4-inches. A thick layer of herbicide-free grass clippings, or weed-free straw to retain soil moisture and suppress weeds.
Leafy greens are shallow rooted and need 1 inch of water per week based on the amount of rainfall recorded in a week. They can be watered using watering cans, soaker hoses or sprinkler irrigation.
Water plants in the morning so that leaves dry during the daytime to minimize incidences of foliar diseases. Higher watering frequency may be needed in sandy and sandy loam soils as compared to clay or clay loam soils.
Aphids can be a problem in leafy greens and can be controlled by hosing leaves when watering and by natural enemies like ladybird beetles. Cabbage worms and flea beetles may also damage plant leaves. To prevent such damage, cover the plants with floating row covers when moths and flea beetles are seen flying in the garden.
Cercospora leaf spot, which causes circular yellow spots on leaves of Swiss chard, collards and kale, is a common disease. Remove infected leaves from the garden and avoid using overhead irrigation.