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.
Life story of a bulb
1. Dormancy (winter) – The plant survives in suspended animation as an underground bulb. Energy is stored in the bulb in the form of starch or soluble sugars, such as glucose.
2. Life returns (spring) – When the plant detects rising temperatures (or returning moisture for dry-weather bulbs), the bulb springs to life. Stored energy is used first to produce roots which can gather moisture.
3. Sprouting (early summer) – Moisture helps the leaf buds to swell, and the stem extends. Once above ground, the green parts can begin to photosynthesize, generating the energy needed for more growth.
4. Flowering (summer) – All this energy is vital to raise the bloom high, so pollinating insects can find it. After pollination, seeds are produced, as a more secure way to spread the species.
5. Preparing for dormancy (late summer) – Once the flower has done its job, the plant begins pumping energy down to the bulb so it can survive winter. Its above-ground parts wither, and the cycle starts over.