A Gardener's Guide to Geophytes

Many gardeners may already know that "bulb" is the name loosely given to specific classification of plants. The botanically correct names for these underground storage organs are geophytes. Bulbs are indeed geophytes, but not all geophytes are bulbs. Botanists might prefer calling them by their anatomically correct name, but the average home gardener and plant lover doesn't mind grouping them all under the "bulb" category for ease.

There are several types of geophytes for the gardener to choose from. It doesn't matter what we call them. They're all fun and easy to grow. Several are even good to eat for humans and critters alike. You just never know when the basic differences in the types of geophytes might be useful, such as impressing a botanist neighbor! More than likely, it might come in handy when it comes time to purchase and plant these little underground gems.

The plant labels won't be so intimidating once you know how geophytes grow and reproduce. Most of us can use a little guidance to be able to distinguish a true bulb from a corm. There are also tubers and rhizomes that are grouped together as geophytes. As if that's not enough, there are also the seasonal issues to contend with. There are spring, summer and autumn flowering geophytes to choose from as well. This is the reason it's important for retail plants to be labeled.

The end result is usually the same no matter the type of geophyte chosen. They're all welcome additions to the garden. Wherever geophytes are planted, a beautiful display will follow for our enjoyment. More often than not, they will include flowers as part of their display. Whether this miniature powerhouse is a bulb or a tuber, they actually have the same purpose. The process in which they do it just differs slightly.

A Geophyte's Function

Bulbs, tubers, rhizomes and corms are similar to food storage systems for the plant. These miniature storage packages named geophytes contain the food and energy for the plant to grow, bloom and finish the life cycle in one year. The foliage for the geophytes plays an important role in the complete process. It's for this reason that the leaves must never be cut down before it completes its cycle. The plants simply will not flower again the next year if the foliage doesn't remain until the photosynthesis is complete.

The leaves of geophytes continue working to manufacture starch and sugars to replenish the supply which was depleted during the flowering process. Corms work in a similar way to bulbs, except they need to manufacture new corms during this process. The original corm withers and new corms are produced. This important process continues for several weeks after the flowers die. This is the reason the leaves must remain until they have yellowed, indicating the process is complete.

Geophytes also vary in cold hardiness. This is another instance when gardeners refer to all of them as bulbs. It's common to hear the terms "cold hardy" and "tender" bulbs, even if they aren't all bulbs. Some of our favorite summer flowering tender "bulbs" are actually corms, tubers and rhizomes.

Hardy geophytes are planted in the fall, survive the winter temperatures and sprout in the spring. Some cold hardy ones must have a period of dormancy with low temperatures before they can sprout again. Tender geophytes are just the opposites. They can be planted when the weather warms in the spring and then dug and stored above freezing temperatures during winter.

Bulbs (photo. 1)

The miniature storage system of a true bulb has everything the plant will need for the plant to survive. A bulb contains a modified stem surrounded by modified leaves and it stores the food and water through cold weather or drought. True bulbs have multiple layers inside them and the very center of the bulb has a miniature version of the flower.

The base of the bulb has a basal plate which serves to hold all of the layers together. This plate is also where the roots emerge. The basal plate at the bottom of the bulb will almost appear hairy.Bulbs reproduce by creating small bulbs that are attached to the parent bulb.

Bulbs can be even further divided into two categories. These are simple differences without much significance for the gardener. Bulbs are classified as scaly and tunicate. The only difference in these is the outside layer or "skin." A tunicate bulb has the papery outer layer and a scale bulb (or non-tunicate) do not. Onion and garlic are examples of tunicate bulbs.

Examples of true bulbs listed with- Common name (botanical name): Amaryllis (Hippeastrum), Daffodils (Narcissus), Grape Hyacinth (Muscari), Hyacinth (Hyacinthus), Dutch Irises and dwarf Iris reticulata and danfordiae, Lily (Lilium), Snowdrops (Galanthus), Tulips (Tulips)

Corms (photo. 2)

Corms have the same protective outer layer just as a true bulb does, but inside they are very different. Whereas a bulb is a totally self-contained plant, a corm is more of a structure that contains the stem for the flower. It is round and solid with a bud on the top. It still stores food for the plant and contains a basal plate just as a true bulb.

A corm will shrivel and die after the flowering cycle is complete and the food stored within is depleted. They do produce more corms to replace the original one. The new corms will grow beside or above the dead corm. This is what still enables a corm to continue its cycle from year to year.

Examples of corms: Crocus, Snow Crocus (Crocus), Elephant's Ear (Colocasia), Freesia, (Freesia), Gladiolus (Gladiolus),

Rhizomes (photo. 3)

Rhizomes are entirely different from bulbs and corms. They are thick underground stems without a basal plate, but they are still geophytes. They grow horizontally under the ground just below or at the surface. Plants with rhizomes usually spread and multiply easily. As they spread, more growth points will develop along the length of the rhizomes.

Examples of rhizomes: Calla Lily (Zantedeschia), Cannas, several classifications of Bearded Iris, Lily-of-the-Valley (Convallaria majalis)

Tubers (photo. 4)

A tuber is a mass of storage tissue in the form of swollen underground stems. A tuber has thick skin and many "eyes" or buds. Each eye represents a growing point where a plant will emerge. It doesn't contain a basal plate. Usually the first plant that comes to mind when describing a tuber is the potato. Don't expect all tubers to resemble potatoes due to their many variances in size and appearance. Not only is our beloved potato a geophyte, but all root vegetables are as well.

Examples of tubers: Begonias (referred to as tuberous begonias), Caladiums, Dahlias