Coleus

Sow coleus seed on the surface of damp soil or seed-starting mix, pressing it in but leaving it uncovered, since the seed needs light and warmth around 70–75°F to germinate; move seedlings to their own pots once they carry two true leaves. Plant out only after frost danger has passed and nighttime temperatures sit in the high 50s to 60s, since cold, wet soil stunts young plants for weeks. Grow coleus in moist, rich, loose, free-draining soil; most types do best in part shade with morning sun and afternoon shade, though some cultivars tolerate heavier sun if kept well watered, while too much shade produces weak, leggy growth. Because coleus like frequent watering, which leaches nutrients, feed regularly with a diluted water-soluble fertilizer such as fish emulsion, but watch plants closely since overfeeding dulls their color. Pinch stem tips regularly to encourage branching and a fuller, bushier plant, and site containers or beds out of strong wind, as the succulent stems break easily. Coleus roots readily from stem cuttings taken from the tips of the plant and set in water or a clean, sterile potting mix.

Indoors, coleus is commonly troubled by aphids, whiteflies and spider mites. In containers, thrips, mealybugs and aphids can cause silvery, gold, yellow or black discoloration on the leaves, though predators outdoors usually keep these infestations from killing whole plants.

Planted directly in the ground, coleus is vulnerable to slugs, which in wet summers can strip entire plants; growing coleus in containers above the soil line helps keep slugs away. Because systemic insecticides used against sucking pests can also harm bees, forceful water sprays or insecticidal soap are preferred controls outdoors.

Cut back flower spikes as they form to keep plants compact, since coleus grown for foliage loses vigor if flowers are left to develop and set seed. Before the first frost, take stem cuttings and pot them up to bring indoors, allowing the plant to be carried over the winter as a houseplant.

Coleus is grown chiefly as an ornamental foliage plant, valued for leaves in shades of green, yellow, pink, red, orange and maroon rather than for its flowers; it is used in landscape beds and borders, hanging baskets, patio containers, and as a houseplant grown in bright light.

In Victorian England, coleus was kept as a parlor plant and became a favorite in "carpet bedding" gardens, where low, equal-height plants were arranged in symmetric, colorful patterns viewed from above alongside plants such as petunias, asters and zinnias.

Coleus traces to tropical and subtropical regions of Asia, with related wild material also found toward northern Australia. Dutch botanists are credited with introducing the plant's foliage to Victorian England in the mid-1800s, where it was rapidly taken up for parlor plants and carpet bedding, beginning its long history in ornamental horticulture.