Tubers, Corms, Rhizomes, and Bulbs... What's the Difference?

Over time, the term "bulb" in gardening terminology has come to describe any type of root form that is planted in the ground to produce a plant. However, only a few of these plants can truly be defined as bulbs. There are four different types of reproductive structures, including Tubers, Corms, Rhizomes, and Bulbs. We'll explain exactly what the true difference is between these four terms!

Tuber

Tubers are formed from a stem or root. They store nutrients that allow the plant to grow the following season. Shoots grow upwards from many different places on the tuber. Examples of tubers are Dahlias, Begonias, Anemones and Potatoes. 

Corm

Corms are actually enlarged underground stems that store nutrients, surrounded by papery outer layers. After stems sprout from the corm, buds form on top of the stem. Corms at their center are solid tissue, whereas Bulbs are immature layers of leaves. At the end of the growing season, a new corm typically grows on the base of the spent one, and plants regrow from new corms each season. Examples of corms are Gladiolus and Crocus.

Rhizome

Rhizomes are stem-like structures that grow horizontally across the ground, forming roots from the bottom while sending shoots upward. Buds form at different parts along the structure, not necessarily at the top. Rhizomes store nutrients for newly growing plants. Examples of rhizomes are Bearded Iris, Canna Lilies, and Calla Lilies.

Bulb

A bulb is comprised of a plant's stem and leaves. The bottom of the bulb is a compacted stem, and roots grow from this part of the bulb. Layers of nutrient-filled leaves sit at the bottom of the bulb and surround a bud that eventually becomes the flower. Examples of bulbs are Tulips, Lilies, and Daffodils.

Whether your plants are growing from a Tuber, Corm, Rhizome, or Bulb, all of these plant structures are sure to produce a spectacular show in the spring and summer months. Happy Gardening!

If you have questions about how to grow these plants, visit The Tool Shed, our source for helpful planting guides! Or, contact us to speak to our team for friendly garden advice.