Imagine an onion. Peel away the outer layers and you’ll find a central core. The onion is a typical bulb. The outer layers are swollen leaves wrapped around a short, flattened piece of underground stem. The swollen leaves protect delicate buds on the core from which new leaves, shoots and roots can grow.
For plants in colder regions, winter is the hardest season to survive. In other countries, the hot, dry summer weather is equally damaging. As the harsh season approaches, bulb-producing plants pump energy-rich starch or sugars down to these subterranean storage organs, while the above-ground parts of the plant wither. The plant then survives below the surface as a bulb, in a state of suspended animation. When better weather returns, the buds sprout and a new plant emerges.
Several bulbs might develop from the original plant, but all new plants are genetically identical to the parent. Seeds, in contrast, mix genes via sexual reproduction, producing new variations.