Description from Flora of China
Morphological characters are the same as those of the family, except: lateral petals always united in pairs into lateral, united petals; fruit a fleshy, explosive capsule; seeds often dispersed elastically from valves when ripe.
Impatiens balsamina (species no. 2) is widely cultivated as an ornamental and medicinal plant. Recently, I. walleriana J. D. Hooker (species no. 4) has become commonly cultivated, and I. usambarensis Grey-Wilson, native to Tanzania, has been introduced.
Taxonomically, Impatiens is a very difficult group. The stem is usually fleshy and succulent, making collected specimens difficult to dry and conserve. The texture of the sepals and petals is very delicate, extremely thin and hyaline. In dried specimens, all of the flower parts are often plicate and coalesced. Although it is difficult to separate and reconstruct the flower parts, determining the shapes and sizes of the sepals and petals, and apices of the anthers (i.e., obtuse or acute), is necessary for identification. To identify and describe every species exactly, we removed flowers from specimens, immersed them in water, and dissected them under a microscope to observe their flower and anther characters clearly. This process is not only time-consuming but also uncertain of success.
The following species were described from China but could not be treated here because no material was seen by the authors: Impatiens huangyanensis X. F. Jin & B. Y. Ding (Acta Phytotax. Sin. 40: 167. 2002), described from Zhejiang; also the following species all described from Yunnan: I. armeniaca S. H. Huang (Acta Bot. Yunnan. 25: 271. 2003), I. austroyunnanensis S. H. Huang (loc. cit.: 276), I. daguanensis S. H. Huang (loc. cit.: 273), I. deqinensis S. H. Huang (loc. cit.: 263), I. lancisepala S. H. Huang (loc. cit.: 277), I. laojunshanensis S. H. Huang (loc. cit.: 268), I. latipetala S. H. Huang (loc. cit.: 278), I. longirostris S. H. Huang (loc. cit.: 261), I. malipoensis S. H. Huang (loc. cit.: 269), I. multiramea S. H. Huang (loc. cit.: 280), I. pianmaensis S. H. Huang (loc. cit.: 267), I. salwinensis S. H. Huang (loc. cit.: 263), I. suijiangensis S. H. Huang (loc. cit.: 274), I. sunii S. H. Huang (loc. cit.: 273), I. wenshanensis S. H. Huang (loc. cit.: 267), I. xishuangbannaensis S. H. Huang (loc. cit.: 271. 2003 ["bannaensis," corrected by S. H. Huang et al., Acta Bot. Yunnan. 26: 574. 2004]), I. yongshanensis S. H. Huang (loc. cit.: 274), I. yui S. H. Huang (loc. cit.: 266), and I. zixishanensis S. H. Huang (loc. cit.: 276).
Species incertae sedis
The following species with united lateral petals are difficult to place taxonomically because either the protologues are too brief or we have not seen the relevant specimens.
Impatiens dichroocarpa H. Léveillé, Cat. Pl. Yun-Nan, 120. 1916.
色果凤仙花 se guo feng xian hua
Plants annual, small, glabrous. Stem erect; branchlets often curved. Leaves alternate; leaf blade gray-green, small, margin aristate-serrate. Inflorescences many flowered. Flowers very small, ca. 5 mm. Lateral sepals linear. Capsule yellow, ca. 2.1 mm.
● Streamsides; ca. 2700 m. Yunnan (Tongchuan).
Impatiens mairei H. Léveillé, Cat. Pl. Yun-Nan, 122. 1916.
岔河凤仙花 cha he feng xian hua
Plants annual, conspicuously hairy. Leaves crowded in upper part of stem; leaf blade 3–6 cm, margin aristate-serrate. Pedicels glandular. Flowers pink. Lateral sepals brown, lateral veins conspicuous, milky-white, margin yellow-brown.
● Meadows; 2600–2700 m. Yunnan (Tongchuan).
This species is hairy except for the flowers. It is related to Impatiens lasiophyton.
Impatiens vaniotiana H. Léveillé, Cat. Pl. Yun-Nan, 122. 1916.
巧家凤仙花 qiao jia feng xian hua
Plants annual, glabrous. Stem erect, branched. Leaves alternate, petiolate, upper leaves sessile; leaf blade 8–10 × 3–4 cm, at least coarsely crenate on terminal margin, aristate. Flowers yellow, large. Lateral sepals conspicuously cuspidate.
● Streamsides on mountains; ca. 3200 m. Yunnan (Qiaojia).
This species is related to Impatiens mairei but differs in that the plant is glabrous with yellow flowers.
More than 900 species: tropical and subtropical mountains of the E hemisphere, some species in temperate Asia, Europe, and North America; 227 species (187 endemic, two introduced) in China; three additional species (all endemic) of uncertain placement.