Annual succulent herb 0.5 - 2.5 m tall Stem: freely branched, pale green, hollow, succulent, and often pale white-waxy (glaucous) on the surface. Leaves: alternate, stalked, blue-green or with a pale white coating, elliptic, less than three times longer than wide, and with round-toothed edges. The leaves of the floral branches are usually over 8 cm long. Flowers: 2.5 - 4 cm long, pale yellow with brownish spots, bilaterally symmetric, spurred, and hanging in small clusters from the leaf axils on slender, drooping flower stalks. Sepals: three, yellow, petal-like. The upper two are small, and the lower one is highly modified into a bowl-shaped (about as long as wide) sac with a narrowed spur. The spur is only up to 6 mm long, hairless, and held at a right angle to the flower body. Petals: five, but irregularly shaped so appearing as three, with a short, wide upper lobe, and the four lower petals fused in pairs to make two, lobed, lateral petals. Stamens: five, but fused above to form a "cap" over the pistil. Pistil: with a five-chambered, superior ovary. Fruit: a slender, long (about 2 cm), hairless, explosively dehiscent capsule with five valves.
Similar species: Impatiens pallida is very similar to I. capensis but that species is a bit smaller, with the leaves of the flowering branches only reaching up to 8 cm long, the flowers are smaller and orange with the opened part of the spurred sepal longer and cone-shaped, and the spur is long, and strongly curved forward and held close to the body of the flower. Impatiens balsamina is quite different in that it is smaller, hairy, has an unbranched stem, almost stalkless leaves with sharp teeth, pinkish flowers, and fuzzy fruit.
Flowering: July to late September
Habitat and ecology: Less common than Impatiens capensis, found in wet and springy places, but preferring calcareous areas and often more shaded habitats. In the Chicago Region one can often find this species in mesic woodlands or shaded floodplains.
Much like no. 1 [Impatiens capensis Meerb.], avg larger; fls 2.5-4 cm, commonly pale yellow, ±dotted with reddish-brown, seldom ochroleucous or white; saccate sep obtuse, nearly or quite as wide as long, the short (4-6 mm) spur abruptly deflexed at about right angles; 2n=20. Wet woods and meadows; Que. and N.S. to Sask., s. to N.C., Tenn., and Okla., mostly less abundant than no. 1, and often in shadier places. June-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.