Kale plants are usually sown into a seedbed in open soil, or in cells or small pots to transplant to their final positions in summer. Five productive plants are often sufficient in a small garden. Early crops to harvest in summer can be sown directly into the soil or in large containers.
SOW IN THE SOIL: Raise young plants for transplanting in a short row 2-3 ft (60-90 cm) long. From mid-spring to early summer, make a drill ½ in (1 cm) deep with a cane or trowel and sow seeds thinly along it. Cover with soil, water, and label the row. Thin seedlings to 3 in (8 cm) when they are big enough to handle. You can sow early crops directly into their final positions from mid- to late spring, in rows 6 in (15 cm) apart.
SOW IN POTS: From mid-spring, fill small pots or cells with seed-starting mix. Sow one seed ½ in (1 cm) deep in the center of each. Cover, water, label, and place in a sheltered spot outdoors or on a bright windowsill.
TRANSPLANT: Plants originally sown in small pots or cells may need potting on into larger containers before they are ready to transplant into their final positions in early to midsummer. Plant out young kale into open soil when plants have five or six leaves. Plant them into well-drained, fertile, slightly alkaline soil. Space plants 18 in (45 cm) apart each way for main overwintering crops or 6 in (15 cm) apart each way for summer leaves. Dig a hole deeper than the root ball, position each plant with its lowest leaves just above the soil surface, and firm the soil around the roots. Thin direct-sown seedlings of early kale to 6 in (15 cm) apart.
WATER AND FEED: Water the seedlings thoroughly after transplanting and keep the soil consistently moist during summer. Weed around plants regularly. Mulch in fall to retain soil moisture and suppress weeds. Feed plants with a high-nitrogen fertilizer in early spring to boost growth.
PROTECT: Kale is fairly problem-free, but netting is a sensible precaution. Cover plants with fine netting or fleece to keep off egg-laying butterflies and pigeons.
Kale leaves are ready to harvest when they are about the width of an adult’s hand. Start harvesting early crops of summer kale three months after sowing, and main winter crops in late fall. Cut or snap the leaves from the base of the stem upward and pick evenly across all your plants. Kale will continue to grow slowly from the top of the leaf cluster during mild winter weather and some varieties put out tender side shoots in spring. Stop picking when flower stems appear, and the leaves toughen. Chop small leaves raw into summer salads; larger leaves are lovely steamed, stir-fried or added to soups and pasta dishes.