Tubers and Bulbs: How to Differentiate Between the Two Geophytes
A well laid-out garden will likely feature a variety of plants, from perennials and annuals to shrubs and even edible flowers, each bloom growing from a distinctive seed. One unique seed structure is the flower bulb, but flower bulbs are often used to denote a variety of types of bulbs. According to the New York Botanical Garden (NYBG), true bulbs, corms, tubers, and tuberous roots are all often considered bulbs, but they're each unique. Structurally, the function of tubers and bulbs is the same: They are both underground storage systems that produce flowers and foliage by stockpiling nutrients for plants. Ahead, we're sharing the differences between bulbs and tubers so you can figure out the proper way to care for your plants.
The Difference Between Bulbs and Tubers
Here's how they differ: A bulb is made up of modified leaves whereas a tuber is a modified stem. Bulbs and tubers have evolved over time to withstand harsh conditions by entering into a period of dormancy. During this period, they draw upon their stored nutrients for survival. According to the University of Illinois Extension, a tuber differs from true bulbs and corms by having neither a basal plant from which roots develop nor a protective tunic-like covering.
The differences can be seen, too. "Evolutionarily, bulbs and tubers serve the same function," says Blythe Yost, CEO and co-founder of Tilly, an online landscaping company. "They store energy in the form of sugars made by the leaves so the plant can get a strong start in the spring. The primary difference is in the appearance—bulbs look like an onion, tubers look like a funky potato or perhaps a hunk of ginger!"
One common example of a tuber is the potato. Some popular flowering tubers are Canna lilies, dahlias, Elephant ears, begonias, iris, and lilies, says Yost. "Tubers cannot be planted with the [same method as true bulbs] and will require a more typical hole to be dug," she says. "The depth and spacing is dependent on variety and desired result." The volume of a tuber is greater than that of a bulb. To divide a tuber, according to the American Dahlia Society, cut it into sections; and make sure you include an eye in every section.
True bulbs, botanically speaking, are typically a subterranean modified stem with leaves complete with flowers in embryonic form, according to the NYBG. One way to see an example of a true bulb is by slicing through it vertically. Bulbs consist of a basal plate from which the roots will grow and a thick, shortened stem surrounded by fleshy scale leaves. These scales contain the food necessary to sustain the bulb during dormancy and early growth, and the basal plate serves to hold these scales together.