Impatiens capensis is an annual herb, 0.5-1. 5 m tall, nodes swollen, stems branched, juicy, rather translucent, waxy-pale green, internodes hollow; roots associated with VA mycorrhizas (Brundrett and Kendrick 1988).
Leaves alternate, stalk to ca 5 cm long (Yatskievych 2006), blade 3-10 cm long, soft textured, waxy-pale below, margin toothed.
Flowers of two kinds, those of large plants orange with darker spots, showy, conical, to 3 cm long, bilaterally symmetric, petals fused, appearing as 3, one above, two below, sepals 3, petal-like, two small laterals, the lower forming a spurred conical cup, spur 0.7-1.0 cm long, hooked forward; ovary superior, stamens 5 short, fused, pollen produced before stigma is receptive, ensuring outcrossing of open flowers (Schemske 1978); nectar taken by ruby-throated hummingbird, Archilochus colubris (Waser 1983), also visited by bumblebees, Bombus vagans and B. terricola (Lovell 1918); large and small plants also produce small, closed flowers that self-pollinate, ensuring seed production for plants in dry or shady habitats, (Waller 1980; Simpson et al.1985); inflorescence of 1-3 axillary flowers, drooping from stalks 2-3 cm long; blooms and fruits June-Sept.; closed flowers produced from about July to frost.
Fruit a narrow, fleshy capsule to 2 cm long, with 5 valves, twisting open explosively when touched, dispersing seeds locally, seeds also dispersed to distant sites by water.
Wetland status: FACW.
Frequency in NYC: Common
Habitat: Wet soil of swamp forests, shady or open marsh and stream edges. Often forming dense monocultures. Soil pH 6.4-7.4 (USDA, NRCS 2006); found in soil pH 5.6-7.0 (Gargiullo unpublished data).
Notes: Yellow flower color is due to a carotenoid pigment (Lovell 1918, Harborne 1988). Seedlings, with rounded leaves, may carpet wet soil in early spring, enables an annual plant to exclude perennial seedling from taking over the site (Windsor 1983). Time for seed development from flower bud to seed dispersal to 48 days for open pollinated flowers, less for self pollinated, (Schemske 1978). Bumblebees cut holes in jewelweed spurs to rob nectar. Honey bees also take nectar from holes in spurs (Lovell 1918). Seeds eaten by birds and mice (Martin et al. 1951). A number of beetle, fly, Lepidopteran and other larvae feed on leaves and other parts in the Midwest (Schemske 1978).