Flora of New Zealand Series

dahlia

Erect or somewhat lax perennial herb, up to c. 1.5 m tall, with tuberous roots. Stems glabrous or sparsely clothed in short hairs, branched above at flowering, dying back to tubers in winter. Lower cauline lvs petiolate, glabrous or sparsely clothed in short hairs, simple or 1-2-pinnate with 2-3 primary pairs and each of lowest pair with 1-5 leaflets; petiole with 2 lateral angles or short wings on upper surface; leaflets mostly not lobed, sometimes 2-3-lobed, sessile, ovate to elliptic, acute to acuminate, coarsely serrate, 5-15-(25) cm long. Upper cauline lvs 3-foliolate or simple. Capitula c. 5-15 cm diam., erect or horizontal. Outer involucral bracts (4)-5-(7), glabrous, elliptic-obovate to spathulate, 15-25 mm long, recurved at anthesis; inner bracts 8, ovate-triangular, usually membranous at margin, 15-25 mm long. Receptacular scales ovate-triangular, obtuse to subacute. Ray florets 8-numerous; ligules yellow, orange, pink to deep red, or pale to deep purple. Disc florets numerous or partly or wholly replaced by ligulate florets, yellow, orange or tinged red. Achenes linear-oblong, or somewhat broader toward apex, 12-15 mm long; pappus 0 or of reduced awns < 0.5 mm long.

N.: Waitakere Range, Auckland City, Thames, vicinity of Hutt Valley and Wellington City; S.: Ashley R. (near Rangiora), vicinity of Christchurch, Dunedin.

Cultivated hybrid 1958

Waste places, shaded gullies, cliff bases, rubbish dumps.

FL Dec-Apr.

Dahlia occurs only locally as a persistent garden discard; as fertile forms seed in gardens, it may be expected to spread. A range of ligule colours, as well as both single and double forms, have been collected in the wild. It seems clear that only 2 spp. are involved in the parentage of the cultivated dahlia: D. coccinea has provided the yellow, orange and red parts of the colour range, and D. pinnata the purple [Sorensen (op. cit.); Giannasi, D. E., Bull. Torrey Bot. Club 102 : 404-412 (1975)]. In cultivation dahlias have also been known as D. rosea and D. variabilis. Wild plants have been previously recorded in N.Z. as D. coccinea.