The term “bulb” is used by most people to refer to plants that have underground, fleshy storage structures. Only some of the plants commonly called bulbs actually are bulbs. The general definition of a bulb is any plant that stores its complete life cycle in an underground storage structure. These underground storage structures store nutrient reserves to ensure the plants’ survival.
Tubers, rhizomes, corms, and bulbs actually all serve the same purpose, just in a different way. They are each a storage unit for food that gives the plant the energy it needs to grow, bloom and complete its lifecycle each and every year.
The energy is created and stored by the foliage’s photosynthesis. You’ve probably heard that it’s important not to cut back the foliage after the bloom has died. That is because the leaves need to have time to absorb energy for next year’s bloom. Each storage system takes differing amounts of time to perform this task. Examples would be Alliums and Daffodils.
Bulbs or bulb-like plants are usually perennials. They have a period of growth and flowering. This is followed by a period of dormancy where they die back to ground level at the end of each growing season.
As with perennials, there are bulbs that are hardy in our climate and others that must be overwintered as house plants or placed in dormant storage.
Bulbs can be broken down into five types of storage structures. These include: true bulbs, corms, (stem) tubers, tuberous roots and rhizomes.