Traditional New Guinea impatiens are easily grown in evenly moist, organically rich, well-drained soils in part shade. Morning sun with afternoon shade is best. Tolerates full shade. Needs protection from full sun, particularly in climates with hot and humid summers. Plants perform well in raised beds where soil is well aerated. Pinch back stems of young plants to encourage branching and/or compact growth. Sheer plants in mid-summer that become leggy. Plants are winter hardy to USDA Zones 10-12. Unless a particularly special or unique plant is involved, most gardeners north of Zone 10 simply purchase cell packs in spring, enjoy the long flowering season, allow the plants to succumb to frost in fall, and then purchase new plants the following spring. If a prized impatiens is to be overwintered indoors, it should be sheared back, brought indoors before temperatures dip into the 40 degree F range, placed in a full sun area (sunny windowsill is similar in light intensity to sun-dappled shade outdoors), and regularly watered. Plants may be propagated by cuttings unless the cultivar in question has a plant patent or patent application pending.
Impatiens hawkeri, commonly called New Guinea impatiens, is a very popular bedding plant in the U. S. today. It is a broadly defined species that is native to New Guinea, the Solomon Islands and New Ireland. It was first collected by Lt. Hawker (hence the specific epithet) in Papua, New Guinea in 1884, but was not introduced into the U. S. until the early 1970s. New Guinea impatiens for the most part features larger plants, larger flowers and better performance in part shade areas than the popular standard impatiens (Impatiens walleriana). They are commonly grown in part shade to shade areas, with little tolerance for full sun. Leaves are in whorls of 3 to 7 leaflets. Oval to elliptic leaflets (2-4" long) are dark green to bronze to variegated. Flattened 5-petaled flowers come in a variety of colors including white, pink, orange, red, violet, and purple. Plants typically grow to 6-18" tall. Flowering is non-stop from May to October. New Guinea impatiens have now been developed into a huge number of different cultivars some of which have been introduced as part of named series.
Although plants native to New Guinea are variable in terms of flower/foliage color, plant size and leaf shape, those plants are now generally considered to be all included within 15 informal groups (natural variability within a single species) as part of a broadly defined Impatiens hawkeri. Former separate species once identified for New Guinea impatiens (e.g., I. schlecteri and I. mooreana) and hybrids between such different species of New Guinea plants (known as New Guinea hybrids) are no longer recognized.
Genus name comes from the Latin word meaning impatient in reference to the explosive discharge of seeds in fall which occurs when mature seed capsules are touched (hence the additional common name of touch-me-not).
No serious insect or disease problems. Plants are reportedly highly resistant to downy mildew. Potential disease problems include impatiens necrotic spot virus, fungal blights, powdery mildew, and rots. Potential insect problems include aphids, mealybugs, thrips, whitefly, slugs and snails. Watch for spider mites. Foliage will typically scorch in too much sun for most plants in this genus, but not for plants in the sun-loving SUNPATIENS SERIES.
Mass or group in beds and borders. Tall ground cover. Edging along walks or paths. Containers, window boxes and hanging baskets. Houseplant.