Types Of Bulbs – Tubers, Rhizomes, Corms And Bulbs

By Heather Rhoades

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 bulb types. Put these frustrations at ease. This article will help explain different types of bulbs.

Garden Bulb Varieties

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 necessary to become a beautiful flower.

Difference Between Bulb Types

Now that we’re clear on what bulbs are and their purpose, let’s take a look at how they differ. Before we get to the different garden bulb varieties, you should know that 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.

Here are the various types of bulbs.

Bulbs

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.

Examples of true bulbs include:

  • Tulips
  • Daffodils
  • Narcissus
  • Amaryllis

Corms

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 are:

  • Crocus
  • Gladiolus
  • Freesia

Tubers

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 include:

  • Dahlias
  • Daylilies
  • Caladiums
  • Anemones

There are also tuberous roots, like tuberous begonia, which are thickened roots that hold food sources.

Rhizomes

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 would be:

  • Calla Lilies
  • Cannas
  • Bearded Iris
  • Water Lilies

Although it may seem like a lot of information, these are just the basics about each of the unique storage systems of garden bulb varieties. 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!

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