The alien flora of Sikkim Himalaya is presented based on field

visit, literature survey and herbarium consultation. As many as

334 alien plant species were recorded under 224 genera and 62

families. The families with maximum number of alien species

were Fabaceae (57 spp.) followed by Asteraceae (49 spp.),

Solanaceae (30 spp.), Poaceae (21 spp.), Amaranthaceae (15

spp.) and Malvaceae (13 spp.). As per the growth forms,

herbaceous species are predominant (54.19%). The available

information suggests that the majority of the species (208 spp.)

have been introduced into the region intentionally for various

reasons, chiefly from the region of American continent. Of the

alien species, 34.43% are invasive and others are either casual or

naturalized. These invasive aliens are chiefly from Asteraceae

(e.g. Ageratina adenophora, Ageratum conyzoides, Bidens pilosa,

Chromolaena odorata, Mikania micrantha and Tridax

procumbens). These species are largely concentrated near human

habitations, roadsides, disturbed areas, forest clearings, riparian

and scrub habitats. The study provides the scientific names

under their families, growth form, habitat, mode of introduction,

invasion status and native range of the alien plant species

recorded.