Horticulture News: Planting time for spring bulbs has arrived

By Kim Cowherd Published:

Fall has arrived and gardeners’ thoughts turn to planting spring flowering bulbs. The following information from Sharon Bale, retired UK Extension Floriculture Specialist, will help you with selection of bulbs and give you some tips for successful planting.

The term “bulb” is used to describe not only a true bulb, but corms, rhizomes, tubers and tuberous roots as well. While horticulturists like to be technically correct when discussing various plants, most home gardeners do not worry about being that precise. Home gardeners need to be aware of differences in plant structures when determining a specific plant’s culture. The following definitions may be helpful.

Bulb: An underground storage structure consisting of a short stem and fleshy scale leaves surrounding a bud. The scales are attached to a tough flat disc or basal plate. Roots arise from this basal plate. Most bulbs have a covering of dry leaves called a tunic. Tulips and lilies are examples of true bulbs.

Corm: Similar to true bulbs. A swollen stem base acts as the food reserve and the buds are generally found on the surface of the corm. Crocus and gladiolus are common corms.

Tuber: An enlarged underground stem with latent buds from which the plant emerges.

Tuberous root: An enlarged underground root with buds located near the collar or base of the stem.

Rhizome: An enlarged underground horizontal stem that is generally thinner and more elongated than tubers. Generally located at or just below soil level. Tall bearded irises are familiar plants with rhizomes.

Bulbs are classified as tender or hardy. Hardy bulbs tolerate, and often require, periods of cold temperature to produce flowers. Tender bulbs will not tolerate cold temperatures and need to be lifted and stored before cold weather damages them. Some tender bulbs may overwinter if the season is mild.

Most bulbs will tolerate a wide range of soils. In general, soil type is not as important as soil drainage. Avoid planting in soils with poor drainage because bulbs may rot. Most bulbs prefer a full sun location.

Bulbs and corms are generally planted at a depth equal to two to three times the diameter of the bulb. Soil type affects planting depths. Bulbs should be planted deeper in sandy soils than in clay soils. Planting depth for rhizomes and tubers is more specific to the particular plant.

Bulbs generally grow in a cycle. At planting time they begin to produce a root system. Spring blooming bulbs should be planted early enough in the fall to allow enough time for the root system to be produced before cold soil temperatures reduce plant growth. Some hardy summer flowering bulbs, such as lilies, can be planted in fall or spring.

All tender bulbs should be planted in spring after danger of frost has passed. Generally, bulbs are only available for sale at their proper planting time. For example, tulip bulbs are not available in spring and dahlias aren’t offered in fall catalogs.

Water bulbs thoroughly at planting time. This establishes good contact between soil and bulb and initiates root growth sooner. Water bulbs in times of drought. Most bulbs do not require a fertilizer application at planting.

Purchase bulbs from a reliable dealer. If an advertisement seems too good to be true, it probably is.

Ads for a large number of bulbs at an incredibly low price usually indicate that small bulbs are being offered. These small bulbs may or may not produce blooms.

When purchasing bulbs, choose ones that have no bruising and feel firm and “heavy.” Bulbs that feel “light” by comparison may have dried out and will not likely produce a desirable plant. The tunic (like an onion skin) on true bulbs may not be intact. This does not indicate an inferior bulb.

For additional information, log on to http://www.ca.uky.edu/agc/pubs/ho/ho80/ho80.pdf. Or call the Extension Office, 695-9035, and ask for publication HO-80.


If you would like to learn more about bulbs, call the Franklin County Extension Office, 695-9035, and sign up for this month’s Gardener’s Toolbox class, “Bulbs and Tubers and Corms, Oh My!” The class is on Tuesday, Oct. 30, 5:30-7:30 p.m. There is a fee of $10 and participants will take home a bulb collection to plant. Class size is limited and pre-registration is required.

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