Perennial herb to 3 m tall, rhizomatous, hairy. Stems erect, stout, branched above. Lower leaves ovate, to 70 cm long, to 25 cm wide, margins toothed and undulate, petiolate. Upper leaves smaller, sessile, stem-clasping. Capitula radiate, in corymbs or racemes, to 8 cm across; summer. Ray florets to 3 cm long, yellow. Disk florets yellow. Achenes 3-5 mm long, angled, glabrous or hairy at apex.

Europe, Asia

 

I. ensifolia L. from Europe is an erect perennial herb to 60 cm tall with glabrous, prominently veined leaves, radiate capitula to 6 cm across and ray florets to 2.2 cm long - 'Gold Star' grows to 30 cm tall with golden flowers;

I. magnifica Lipsky from the Caucasus is an erect perennial herb or subshrub to 2 m tall with ovate leaves that are hairy below, radiate capitula to 15 cm across and ray florets to 2 cm long; 

I. orientalis Lam. from the Caucasus is an erect perennial herb to 60 cm tall with ovate to oblanceolate leaves that are yellow-hairy, radiate capitula to 8 cm across and ray florets to 2.5 cm long - 'Grandiflora' is a variant of the species. [I. grandiflora Willd.]

Source: Lawson, L.; Spencer, R. (2002). Dahlia. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 4. Flowering plants. Dicotyledons. Part 3. The identification of garden and cultivated plants. University of New South Wales Press.