Dahlia are tuberous rooted perennials with pinnately divided leaves and showy flower-heads, double in many cultivars, in summer and autumn
Miniature-flowered Decorative dahlias have fully double flowerheads up to 10cm across, with flat or slightly incurved florets
'Gallery Art Nouveau' grows to 75cm, with loosely double flowers 10cm diameter, the outer florets bright pink, streaked with deep red, the inner deep purplish-red