DC.
Description
Erigeron karvinskianus, the Mexican fleabane, is a sprawling daisy native to Mexico and Central America but now naturalised across much of the temperate and subtropical world. GBIF documents it from Britain, France, the Netherlands, Spain, Italy, the United States, Mexico, New Zealand, Australia, South Africa, Japan and India, among many others, with over 67,000 occurrences reflecting its status as a cosmopolitan introduced species. It colonises walls, rocky banks, paths, terraces and disturbed slopes from sea level to about 2500 m. The plant illustrated was photographed near Sambon in the Sikkim/West Bengal hills at 1750 m in April, where it has become established as a garden escape along walls and roadsides.
It is a slender, much-branched, mat-forming perennial with wiry, decumbent to ascending stems. The lower leaves are oblanceolate and few-toothed or trilobed, the upper entire and reduced. The numerous small capitula are borne on slender peduncles; each head has a single series of narrow ray florets that open white and age through pink to purplish-red, so that a plant simultaneously bears flowers of several hues, surrounding a central disc of yellow tubular florets. The fruit is a small ribbed achene crowned by a pappus of fine bristles that facilitates wind dispersal.
A member of tribe Astereae, E. karvinskianus is valued horticulturally for its long, profuse flowering and self-seeding habit, the very trait underlying its weediness. In parts of Australia, New Zealand and South Africa it is regarded as an invasive environmental weed escaping gardens to colonise native rock and cliff habitats. In the Himalaya it is a naturalised alien rather than an indigenous element, of no conservation interest but of some invasion-ecology concern.
Author: DC. · Sources: POWO (Kew), GBIF, Flora of China, Flora of North America, Annotated Checklist of the Flowering Plants of Nepal, Erigeron (Asteraceae: Astereae) systematic monograph