INFORMATION ABOUT TUBERS, RHIZOMES, CORMS AND BULBS…
Tubers, rhizomes, corms, and bulbs, OH MY! If you’re new to gardening then it’s a pretty safe bet that you’re feeling a little daunted by all of this terminology. Even some veteran gardeners may not be completely sure of the difference between tubers, rhizomes, corms, and bulbs.
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. Well, that’s because the leaves need to have time to absorb energy for next year’s bloom.
Basically tubers, rhizomes, corms, and bulbs are each a little package containing everything needed to become a beautiful flower. Now that we’re clear on that, let’s take a look at how they differ:
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.
Not to further complicate matters, but bulbs can be separated into two categories – scaly bulbs and tunicate bulbs. This is actually a quite simple distinction – tunicate bulbs have that papery, scale like skin, and scaly (or non-tunicate) bulbs do not.
Also, there are hardy bulbs and tender bulbs. Hardy bulbs, like tulips and daffodils, are planted in the fall and will come up in the spring. The reason they are called hardy is because they can survive the winter’s cold weather. Tender bulbs, like dahlias and begonias, are planted in the spring for summer blooming. They cannot withstand the winter and must be dug up and stored in a cool dry place.
Examples of Bulbs – Tulips, Daffodils, Lilies, Narcissus, Amaryllis
Corms 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, Tuberous Begonias
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
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
Although it may seem like a lot of information, I’ve shared just the basics about each of these unique storage systems. For such small things, tubers, rhizomes, corms, and bulbs are actually quite complex. They really weren’t kidding when they said that great things come from small packages!