Impatiens

Sowing: Seed is started indoors 8 to 12 weeks before the last frost, scattered on the surface without covering since light aids germination, and kept at 70–75°F with seedlings emerging in 14 to 21 days; young plants are hardened off and moved outdoors only after the last frost has passed.

Siting and watering: Impatiens performs best in part to full shade, tolerating some sun only with steady moisture, since too much sun scorches the leaves; it wants a moist, well-drained soil rich in organic matter and slightly acidic. Beds are watered about once a week in dry weather while container plantings are checked more often, and overwatering can cause the roots to rot.

Feeding and maintenance: Container plants are fed every two weeks with a water-soluble fertilizer, while bedding plantings are given a slow-release fertilizer worked into the soil before planting. Plants that grow leggy by late summer can be trimmed back by about a third to encourage new growth, and stem cuttings taken in fall root readily in potting mix for replanting the following spring.

Pests: Impatiens has no serious insect or disease problems overall, though it can attract aphids, spider mites, nematodes, slugs, and snails, and deer may browse the foliage.

Diseases: It is susceptible to downy mildew, caused by the organism Plasmopara obducens, which does not respond to fungicides used against true fungal diseases; other problems include powdery mildew, verticillium wilt, rhizoctonia web blight, root rot, viral leaf spot, and seedling damp-off. Plants wilt in hot, dry spells and need extra water then, but soggy soil or overwatering can cause rot.

Seed pods form and ripen from late summer into fall, and when mature they burst open explosively, scattering seed away from the plant, a trait that gave the genus its name. Gardeners can gather seed from the pods before they split, or let the plants self-sow where they stand.

Impatiens is grown chiefly as an ornamental bedding plant, filling containers, hanging baskets, and window boxes and massed along shady borders, under trees, or in woodland-style plantings; some are also kept as houseplants indoors.

Impatiens walleriana is native to East Africa, found wild as a subshrub of wet tropical habitats in Kenya, Mozambique, Tanzania, and Zimbabwe; the species was first described from a specimen collected in Mozambique in 1864. It is not native to North America, where it has instead been introduced and grown as a garden ornamental.