Lobelia purpurascens is a small, smooth herb usually less than high with ascending or more or less prostrate stems, usually long with white
rhizomes. The leaves are arranged alternately, more or less
sessile, elliptic to oval shaped, long and wide, margins toothed and the undersurface usually purplish coloured on a
petiole up to long. The single flowers are borne in leaf axils on a
pedicel long,
corolla pale mauve-pink, bluish or white, long, lower petals oblong-rounded, upper petals upright, tapering to a point, curved inward and smaller than upper petals. Flowering occurs from November to May and the fruit long, wide and smooth. ==Taxonomy and naming==