Perennial flower tubers. Marble Ball Dahlia are unique and eye-catching purple and white flowers in ball/pompom shapes. Perfect for displaying in pots, planters, beds, borders and cut flowers too, this will definitely add a statement to the garden, great for pollinators. Recommended by the Nation Dahlia Society. Soil: moist but well-drained Sunlight: Full sun or very partial shade Planting period: Spring Flowering: Summer/Autumn Flowering Height: 60-90cm (12-24in) Placement: Just under surface Material: Other Material.