Annual succulent herb 0.5 - 1.5 m tall Stem: branched above, light green, translucent, hollow, and succulent. Leaves: alternate, stalked, egg-shaped, less than three times longer than wide, and with round-toothed edges. The leaves of the floral branches reach up to 8 cm long. Flowers: 2 - 3 cm long, orange with red-brown spots (rarely lemon-yellow, white, or without spots), bilaterally symmetric, spurred, and hanging in small clusters from the leaf axils on slender, 2 - 3 cm long, drooping flower stalks. Sepals: three, orange, petal-like. The upper two are small, and the lower one is highly modified into a cone-shaped (longer than wide) sac with a narrowed spur. The spur is more than 6 mm long, hairless, strongly curved forward, and held close to the body of the flower. 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, 2 cm long, hairless, explosively dehiscent capsule with five valves.
Similar species: Impatiens capensis is very similar to I. pallida, but that species is a bit larger, with the leaves of the flowering branches exceeding 8 cm long, the flowers are larger and pale yellow with the opened part of the spurred sepal shorter and bowl-shaped, and the spur is short, divergent, and pointing down from 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: June to late September
Habitat and ecology: Common, typically in wet or springy open places such as calcareous fens, marshes, and lake shores, but also occasionally in upland woods and even sometimes in somewhat disturbed wet areas such as ditches. Often thriving in open sunny areas as long as the soil is moist.
Glabrous annual, 5-15 dm, branched above; lvs soft, pale or glaucous beneath, ovate or elliptic, 3-10 cm, crenate-serrate with mucronate teeth, on long wingless petioles; racemes widely spreading, few-fld; fls drooping on slender pedicels, 2-3 cm, commonly orange-yellow, thickly spotted with reddish-brown, rarely lemon-yellow or white, or without spots; saccate sep conic, the slender spur 7-10 mm, curved forward close to the body; capsules 2 cm, dehiscing explosively when jarred; 2n=20. Moist woods, brooksides, wet roadside ditches, and springy places; Nf. and Que. to Sask., s. to S.C., Ala., and Okla. June-Sept. (I. biflora; I. nortonii)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.