Culture
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. Trim back 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°F range, placed in a full sun area (sunny windowsill is similar in light intensity to sun-dappled shade outdoors), and regularly watered.
Noteworthy Characteristics
Hybrid New Guinea impatiens are a group of impatiens that result from crossing the species Impatiens hawkeri with other closely related species of impatiens such as I. platypetala and I. aurantiaca. Hybrid New Guinea impatiens are a very popular bedding plant. Most selections feature larger plants, larger flowers and better performance in part shade areas than the popular standard impatiens (I. 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 frost.
Genus name comes from the Latin word impatiens meaning impatient in reference to the violent seed discharge from the ripe pods.
'SAKIMP039' is a hybrid selection of New Guinea impatiens that features 2" wide, red blooms and a dense, compact, mounding habit. Flowers freely from late spring to frost. Mature plants will reach up to 2.5' tall and spread to fill a 1.5' area. Commonly sold at nurseries and garden centers under the name SUNPATIENS COMPACT FIRE RED. Plant patent number PP28590 applies to this cultivar.
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, however, with a little extra moisture, cultivars in this group have been grown in full sun with no problems.
Uses
Mass or group in beds and borders, as an edging along walks or paths, or as a tall ground cover. Use in containers, window boxes and hanging baskets. As a Houseplant.