Flowering bulbs are an essential component of the well planned garden or landscape, adding interest and bright colors in a way that shrubbery and other herbaceous perennials cannot.

Like so many things in horticulture, the term "bulb" has taken on all kinds of meanings. A true bulb is a swollen underground bud formed from fleshy scales or leaf bases which acts as a storage unit to enable various plants to rest in a dormant state during part of the year. Bulbs include tulips, daffodils, lilies (not daylilies) and alliums (ornamental onions), iris (some species such as Iris reticulata - others are rhizomes), snowdrops (Galanthus) among others.

Inside a bulb is a small preformed flower called the flower primordium. Given the correct environment, the flower primordia will mature, form a flower bud and bloom. Bulbs that fail to bloom are called "blind."

The flattened base of a true bulb is called the basal plate. It is the area from which all roots originate and should always be planted downward in the soil. Last year's withered stem may linger on the top side of the bulb. An undamaged bulb is often covered by a thin papery sheath or tunic.

Many other plant tissues are commonly, but incorrectly, called bulbs including corms (crocus, gladiolus, windflowers, Colchicum, Freesia, Elephant Ears [Colocasia]), tubers (potatoes), tuberous roots (dahlias, tuberous begonias) or storage roots (Canna).

Corms, from which crocus and gladiolus grow, are actually swollen stems and have nodes, internodes and lateral buds growing from the nodes. A new corm forms atop the old one each year, and clusters of small corms, called cormels, grow around the base. Flowering stems grow from several buds on top of the corm.

On very flat corms, such as those of Anemone, it may be quite difficult to distinguish top from bottom. Look for last year's shriveled stem, and plant it upward.

Tuberous roots, such as tuberous begonias and Dahlia, are swollen roots that have one to several eyes at one end near the old stem. Unless an eye is present, a tuberous root plant cannot grow.

Advantages of Bulbs

1) Easy to grow. Most bulbs contain a preformed flower bud and all the food required for blooming when purchased. It takes minimal skill to make bulbs bloom, provided a good site is selected. In addition, bulbs are generally maintenance-free and pest-free when planted properly and given a bit of fertilizer.

2) Colorful. A chief attraction of all bulbs is that they provide color. Spring flowering bulbs provide color from early March, before many trees and bloom, through June, when annuals are planted. Summer bulbs help fill out the garden from June through September.

3) Inexpensive. Most common bulbs are relatively inexpensive. They are considerably cheaper when purchased in quantity, and hardy species can last for many years.

4) Flexible. Bulbs are relatively small and may be moved, if required, so they are flexible landscape components. Bulbs fit in around existing shrubbery, in wooded areas, in rock gardens and in other niches where they add interest to a landscape.

5) Compatible. Bulbs are excellent mixers. They combine especially well with spring flowering perennials. Spring bulbs are often over-planted with annuals to hide their dying foliage.

Hardy vs Tender Bulbs

Within all the plants commonly called bulbs, there is a wide diversity of plant types and growth habits. All of them survive as underground structures that serve as energy storage for the following season's growth.

As with all other types of plants, bulb plants have originated in many different parts of the world with many different climates. Some come from the tropics and others from the more temperate regions with cold winters. So, another classification for bulbs is to divide them into Hardy Bulbs and Tender Bulbs.

As the name implies, hardy bulbs are those that can withstand exposure to subfreezing temperatures of northern winters. Generally, these are bulbs that we plant in the ground and forget. They keep coming back year after year with no special care on our part. Tulips, daffodils, hyacinth, grape hyacinth, winter aconite, lilies, alliums and other common landscape bulbs fall into the hardy group.

Canna lily, Dahlia and gladiolus are a few of the tender bulbs. These are plants that generally developed in tropical areas and have not been adapted to living with cold temperatures. They are planted in the spring and, if you expect to keep them for future years, must be dug up and stored for the winter.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


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