On some plants, this type of rooting structure can be very invasive. Rhizomes differ from other storage structures by growing horizontally under the surface of the soil. The tuberous-rooted begonia reproduces from buds on top of the round, flat tuber. The root should be divided into sections with an eye bearing portion of the stem left with each section of the root. The tuberous root of a dahlia should not be divided before placing in storage in the fall but should be divided at planting time. The dahlia reproduces from buds at the top end of the root or base of the stem. The tuberous root differs from other root structures by the nutrient reserves being stored in an actual root instead of an enlarged stem.
The caladium tuber has buds scattered over the tuber surface from which shoots and roots develop.Įxamples of plants that develop from tubers include caladiums, oxalis and anemones, and the common vegetable, the potato. TubersĪ tuber differs from the true bulb and the corm by not having a basal plant from which roots develop and not having a protective tunic covering. The cormels can be saved and replanted in the back of the garden until they reach flowering size.Įxamples of plants that develop from corms include gladiolus, crocus, and autumn crocus. When the corm is cleaned up and the old stem removed, the growing point of the corm will be evident. The remains of the old corm will be directly beneath the newly formed corms. The newly dug corms will have cormels that are pea size formed around the top of the old corm. When gladiolus corms are dug in the fall, they should be separated into well developed corms, to be stored for replanting, and poorly developed corms that the gardener may want to discard. Examples of plants that develop from corms include gladiolus, crocus, and autumn crocus. The corm contains a basal plate (bottom of bulb from which roots develop),thin tunic and a growing point. A corm does not have visible storage rings when cut in half. CormsĪ corm is a swollen stem base that is modified into a mass of storage tissue. It will take more than one year for the bulbils or bulblets to become flower size. They can also be propagated from bulblets that develop at the base of fleshy lily scales if maintained in a moist sand medium. Lilies can be propagated from bulbils that develop in the leaf axils of the plant. Imbricate bulbs must be kept constantly moist before planting so they are not injured by the scales drying out. The imbricate bulb does not have the tunic (papery covering) to protect the fleshy scales. This is an indication that it is time to dig up and divide the bulbs.Īn example of the imbricate bulb is the lily. When these bulbs become overcrowded,the flowers start to diminish in size. These bulbs, called offsets, develop from buds within the base of the mother bulb and produce new plants. Many plants such as daffodils form new bulbs around the original bulb. Good examples of tunicate bulbs include: tulips, daffodils, hyacinths, grape hyacinths (muscari), and alliums. A tunicate bulb has a paper-like covering or tunic that protects the scales from drying and from mechanical injury.
True bulbs are divided into tunicate bulbs and imbricate bulbs. It contains the basal plate (bottom of bulb from which roots grow), fleshy scales (primary storage tissue), tunic (skin-like covering that protects the fleshy scales), the shoot (consisting of developing flower and leaf buds), and lateral buds (develop into bulblets or offsets). Daylilies and peonies, which are popular plants with gardeners, are examples of this type.
A sixth category of fleshy roots has been added here for the purpose of showing the structure. These include: true bulbs, corms, tubers, tuberous roots and rhizomes. Spring bulbs start to grow again in the fall and flower the following growing season.īulbs can be broken down into five types of storage structures. For spring bulbs, the end of the growing season is in late spring or early summer. This is followed by a period of dormancy where they die back to ground level at the end of each growing season. They have a period of growth and flowering. The definition of a bulb is any plant that stores its complete life cycle in an underground storage structure.īulbs or bulb-like plants are usually perennials.