Gardeners refer to several distinct plant structures as flower bulbs in everyday conversation.
- True bulbs – Rounded, pointed top, flat base where roots grow: Allium, Anemone, Bluebell, Daffodil, Hyacinth, Snowdrop, Lily, Tulip
- Corms – Similar to bulbs, with buds on top and roots from the base: Crocus, Gladioli
- Tubers – Swollen roots like Dahlia, or swollen stem bases: Cyclamen, Aconite
- Rhizomes – Horizontal, swollen stems, growing on or just below the soil: Bearded Irises, Lily-of-the-valley, Cannas
From a planting season perspective, bulbs / corms / tubers / rhizomes are handled one of 4 ways:
- Dry, dormant bulbs are planted in Autumn
- A limited range of bulbs are planted in growth (In the Green), in early Spring
- Tender species like Dahlias are best planted into warm soil in late Spring
- Some late season bulbs like Nerines and Colchicums can be planted until the end of Summer
For convenience, flower bulbs are commonly classified as Spring or Summer flowering.