Dahlia

Perennial herbs or shrubs, rarely scrambling epiphytes, developing tubers or the rootstock tuberously thickened. Most parts of plant aromatic when crushed. Stems erect, rarely vine-like, arising singly, or many in a cluster, the indi vidual stems mostly unbranched except in the flowering portion or rarely branching freely from the base; internodes hollow or solid, sometimes the pith chambered; nodes septate or the septa sometimes incomplete. Leaves opposite or in whorls of 3, petiolate, simple and entire or lobed, to 1–3-pinnate. Inflorescences solitary or aggregated into loose cymes. Capitula pedunculate, radiate, often large, nodding. Involucral bracts free, 2-seriate, strongly dimorphic; outer bracts erect, spreading or reflexed at anthesis, fleshy, dorsally several-lined, herbaceous; inner bracts broader, green to scarious, several to many-lined, translucent. Receptacle flat or nearly so; paleae ovate, obtuse to subacute, scarious. Ray florets female or sterile, numerous, ligulate, apically entire or denticulate, showy, variously coloured, often in shades of white, pink, purple, red, yellow or orange. Disc florets bisexual (innermost sometimes functionally male), numerous, tubular and 5-lobed (or replaced by ligulate florets in many cvs), yellow or purple. Cypselas linear-oblong or spathulate, compressed but not winged, often apically contracted with a thickened cap. Pappus obsolete or with 2 rudimentary awns or filiform bristles.