Dahlia are tuberous rooted perennials with pinnately divided leaves and showy flower-heads, double in many cultivars, in summer and autumn
Small-flowered Waterlily dahlias have double or semi-double flowerheads, with relatively few broad rays, forming a rather flattened flowerhead 10-15cm across
'Glorie van Heemstede' grows to 1.3m in height, with divided foliage and lemon-yellow flowers to 13cm in width