Site. Plant cress in shade or semi shade. Grow garden cress and curly cress in moist but well-drained sandy loam. Grow watercress in a container of compost-rich, sandy soil submerged in running water. Cress prefers a soil pH of 6.0 to 6.8.
Planting time. Cress are cool-weather annuals. Sow cress in the garden early in spring, as early as 4 or 6 before the last frost, or grow cress indoors year round. Cress will germinate in about 14 days at 45°F. Garden cress is quick growing from seed; it will be ready for harvest 15 to 20 days after sowing. Curly cress requires 40 to 50 days to reach maturity but harvest can begin 15 days after sowing. Watercress requires 55 to 70 days to reach maturity but runner tips can be pinched off for use 15 to 20 days after sowing. Sow cress every 10 days for a continuous harvest through midsummer. Cress can become pungent and inedible in hot weather. Plant cress in late summer for an autumn and winter harvest.
Planting and spacing. Sow garden cress and curly cress seed ¼ inch deep; sow seed thickly in wide rows; thin successful seedlings to 6 inches apart. Space rows 18 to 24 inches apart. Sow successive crops every 10 to 14 days. Grow watercress in submerged containers. Pinch back cress to keep it manageable.
Water and feeding. Cress requires even moisture. Do not let roots dry out. Grow watercress in gently running water. Grow cress in soil rich in aged compost.
Companion plants. Bunching onions, chives, peppermint, spearmint, and wintergreen. Cress can be inter-planted with other small crops.
Care. Keep soil weed free. Avoid growing cress in direct sun. Pinch cress back to promote new foliage.
Container growing. Garden cress and curly can be grown in containers, pots and boxes. Sow seeds thickly; cress is not bothered by overcrowding. Garden cress can be grown indoors on a windowsill. Use a container with good bottom drainage. Keep the soil moist.
Pests. Cress has no serious pest problems.
Diseases. Cress has no serious disease problems.
Harvest. Cut or pinch out cress tips as needed, cut-and-come-again. Begin cutting plants when they reach 3 to 4 inches tall. Plants cut back to ½ inch will quickly regrow. Cress is most tender at the early seed-leaf stage; harvest cress well before it matures. Sprouts can also be used fresh.