Tubers, rhizomes, corms, and bulbs actually all serve the same purpose, just differently. They are each a storage unit for nutrients that give the plant the energy it needs to grow, bloom, and complete its life cycle. The energy is created and stored by the photosynthesis of the leaves. It’s important not to cut back the foliage after the bloom has died, because the leaves need to have time to absorb energy for next year’s bloom.
Bulbs (which are referred to as “true bulbs”) grow in layers, much like an onion. At the very center of the bulb is a miniature version of the flower itself. Helping the bulb to stay together is something called a basil plate, which is that round and flat hairy thing (those are the beginnings of roots) on the bottom of the bulb. Bulbs reproduce by creating offsets. These little bulbs are attached to the larger bulb.
Examples of Bulbs: Onion, garlic, lily, tulip, amaryliss, narcissus, and Iris
Corms (or bulbo-tuber, bulbotuber) look a lot like bulbs on the outside but they are quite different. They have the same type of protective covering and a basal plate like the bulb does, but do not grow in layers. Instead the corm is the actual base for the flower stem and has a solid texture. As the flower grows, the corm actually shrivels as the nutrients are used up. Essentially the corm dies, but it does produce new corms right next to or above the dead corm, which is why the flowers come back year after year. Depending on the type of flower, it may take a couple years to reach blooming size.
Examples of Corms – Crocus, Gladiolus, Freesia, Taro
The easiest thing to think of when you’re trying to understand a tuber is the potato. The potato is a tuber that I’m sure we’re all familiar with. A tuber has leathery skin and lots of eyes – no basal plate. All of those eyes are the growing points where the plants will emerge.
Examples of Tubers – Dahlias, Begonias, Caladiums, Anemones, Potatoes, Sweet Potatoes, Water Chestnuts, Yucca root, Yam, Water Lily root
Rhizomes are simply underground stems. They grow horizontally just below the soil’s surface. They will continue to grow and creep along under the surface with lots and lots of growing points.
Examples of Rhizomes – Calla Liles, Cannas, Bearded Iris, Water Lilies, hops, asparagus, ginger, Lily of the Valley
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. Define root as a part of a plant body that bears no leaves, and therefore also lacks nodes. The three major functions of roots are 1) absorption of water and inorganic nutrients, 2) anchoring of the plant body to the ground and 3) storage of food and nutrients
The term root crop refers to any edible underground plant structure, but many root crops are actually stems, such as potato tubers. Edible roots include cassava, sweet potato, beet, carrot, rutabaga, turnip, parsnip, radish, yam, and horseradish. Spices obtained from roots include sassafras, angelica, sarsaparilla, and licorice
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