6 Common Types of Bulbs

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6 Common Types of Bulbs

Add Flower Bulbs for Early Spring Color and Great Summer Blooms Too

If you are a gardener, you have probably heard the term “bulb” thrown around a lot. In this article, we cover the most common types of bulbs that you encounter as a gardener, how to recognize them and how to choose the ones that are best for you. We hope that this information will help you choose the type of bulb that fits your gardening goals. Before we discuss the types of bulbs, let’s briefly dig into what a plant bulb actually is.

What are Bulbs Anway?

Bulbs are enlarged underground storage structures used during the dormancy stage as food storage organs. Bulbs contain the genetic material for a flower bulb to reproduce, as well as carbohydrate sugar to feed the plant as it starts to grow and develop roots and leaves.

Bulbs exist primarily to help the plant endure harsh conditions. Gardeners plant bulbs at a depth required by the species (see chart below). The bulbs sprout roots first and then start their ascent to the surface. It can take a while, so if this is your first bulb planting season, be patient!

There are two types of true bulbs: tunicate bulbs and imbricate bulbs. However, most gardeners also refer to corms, tubers and rhizomes as bulbs, too.

True bulbs have layers inside surrounding the developing plant shoot and are covered with the protective outer papery skin. There is a basal plate, which is where the roots form. 

Tunicate bulbs have an outer skin. This tunic protects the inner layers which hold the energy supply for the developing plant. A tulip is a good example of this type of true bulb. Imbricate bulbs do not have the outer layer to protect them. These bulbs need to be kept moist prior to planting. Lilies are an example of an imbricate bulb. This is the second type of true bulb. There are several other types of fleshy “bulbs.” While not true bulbs as described above, they are commonly referred to as bulbs.

Corms are similar to true bulbs, but they are solid inside. Corms also have a basal plate which the roots will grow from. Gladiolas, crocus and crocosmia grow from corms. Tubers are a swollen stem with “eyes” or growth nodes. When planting a tuber, it should have three eyes to assure a good plant start. Daylilies and cyclamen grow from tubers, as well as potatoes.

Rhizomes are thickened underground stems that will sprout new growth and provide energy for the shoot while they develop. An iris is a good example of a rhizome. Bamboo is also grown from a rhizome. Tuberous roots are roots that swell to hold a food supply for the growing plant. A tuberous begonia is an example of a plant with tuberous roots.

Bulbs that bloom in the spring are planted in the previous fall, while the fall blooming bulb flowers are planted in spring or early summer. A good bulb planting chart will help you determine when to plant your bulbs.

Flower bulbs can be “forced” to bloom out of season. These include the amaryllis, which has become a favorite at Christmas time, and the spring flowering bulbs like tulips, hyacinths and daffodils, which are often found in full bloom for the Easter season. You can do this yourself, as it is not difficult. Tulips, daffodils, crocus, hyacinth, snowdrops and iris all need to have a cool period before they start to grow.

Simply plant the bulbs in a pot that is deep enough for there to be at least two inches of soil beneath the bulbs. There should be a drainage hole in the bottom of the pot. Fill the pot with a loose potting mix. Plant tulips, daffodils and hyacinths with the tips of the bulbs just peeking out of the soil. The smaller bulbs can be buried in the pot. Plant close together–just don’t let them touch.

Water well so that the water is seeping through the drainage holes. Place pots in a cool place. The temperature should be between 35 and 50 degrees. Usually, a garage or basement will be cool enough. Check the top inch of soil for dampness. Water when the soil is dry below one inch.

Bring your pots into a cool room with dim light to start. When the shoots start to show, usually in about a week, move the pot into a warm sunny room.

Two bulbs do not require a cool down period: the amaryllis and paperwhites. Place these bulbs in shallow water and let the roots soak for a few hours. Plant the bulbs in loose potting soil with the top two-thirds of the bulb showing. Both of these flowers grow quite tall so a support will be helpful.

Add flower bulbs, both indoors and out, for some early spring color and great summer blooms as well as seasonal beauty.