Wall.
Description
Lobelia rosea is a slender annual or short-lived herb of the eastern Himalaya and Indo-Burmese region, ranging from Nepal, Bhutan and north-east India through Myanmar, Thailand, Laos and Vietnam to southern China and peninsular Malaysia. GBIF records 112 occurrences across this subtropical to warm-temperate arc. It favours moist open ground, stream and paddy margins, damp grassy banks and disturbed clearings at low to middle elevations. The plant from Mulabari in Gorkha, central Nepal, at 1340 m in May is a typical pre-monsoon population on humus-rich soil in light shade.
It is a delicate herb with erect or ascending, simple or sparingly branched stems exuding milky latex when broken. The leaves are alternate, sessile or shortly petiolate, ovate to lanceolate, serrate to denticulate and thin in texture. The flowers are borne in lax terminal racemes on slender pedicels. The corolla is markedly zygomorphic and two-lipped, pink to rose-purple (whence rosea), the tube split dorsally and the lower lip three-lobed; the five anthers are connate around the style into the Lobelia tube, the two lower ones tufted apically. The fruit is a small two-valved capsule dehiscing apically to shed numerous minute, reticulate seeds.
Lobelia, the largest genus of Campanulaceae (subfamily Lobelioideae), is sometimes segregated, but molecular evidence supports its retention within an expanded Campanulaceae. L. rosea belongs to a group of small-flowered Asian annuals delimited chiefly by corolla colour, leaf shape and capsule form. Like its congeners it contains piperidine alkaloids, and several Asian Lobelia species feature in traditional medicine. Widespread and weedy, persisting readily in disturbed seasonally moist habitats, it is of no conservation concern.
Author: Wall. · Sources: POWO (Kew), GBIF, Flora of China Vol. 19, Flora of Bhutan Vol. 2, Annotated Checklist of the Flowering Plants of Nepal, Lammers world checklist of Campanulaceae