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Rhizomes and Tubers
and Corms, Oh My!

A Guide to Summer Flowering Bulbs in Kansas City

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Bulbous plants in the garden can provide years of enjoyment if you follow the few steps listed below. Summer flowering bulbous plants are called many things: Tubers (begonia), corms (gladiolus, crocus, and freesia), tuberous roots (ranunculus and dahlia), and rhizomes (cannas and callas).  For simplicity we will use the term bulb to refer to each of them.

Plant large masses of bulbs to appreciate the beauty. Before planting, and to help determine your needs and keep the plants in harmony, visualize what will be in leaf or bloom at the same time as the bulbs.

It is important when landscaping with bulbs to plant groups of 12 or more of the same variety. Massed flowers look better; avoid the polka dot or soldier effect.

When buying bulbs, always select ones that are firm and blemish-free. Remember, large bulbs produce large flowers.

Planting Time
Plant summer-flowering bulbs after danger of spring frost. In Kansas City the first full weekend in May is a safe bet.

Bed Preparation
Where a large number of bulbs are to be planted, prepare the beds to a depth of 9 to 12 inches. Uniform bed preparation permits a uniform planting depth that helps insure uniform flowering.  Plant in well-drained soils.

Don't guess, soil test - Bulbs grow and flower best with a soil pH between 5.5 and 7.0. Phosphorus is important for proper root and flower development, and since phosphorus is not mobile in the soil, add it to the soil before planting.  For summer-flowering bulbs, apply 5-10-10 at 2 pounds per 100 square feet three times during the growing season at 6-week intervals.

If you plant bulbs with a bulb planter or trowel, apply one teaspoon of bone meal to the bottom of the planting hole 1 to 2 inches below the bulb.

Summer-Flowering Bulbs

Begonias - Select an area that is well drained and partially shaded. Set the tubers in the ground just so they are covered and no deeper, because they are subject to rotting. To allow for plenty of growing space and air circulation, set the tubers or plants 18 to 24 inches apart.  It may be necessary to stake the young plants because many of the larger growing varieties become top heavy in bloom.

Dahlias - Dahlias are among the easiest garden plants to grow. The plants flower in virtually every color except clear blue, and flowers range in size from less than 1 inch across to those more than a foot in diameter. Plants normally bloom from midsummer until frost. The fleshy roots must be dug and stored each year. Many varieties can be started from seed. When propagating roots, be sure that a portion of the old stem remains attached. This insures bud development of the new plant.

Gladioli - Gladioli offer a wide array of colors and are often grown as cut flowers. The plants grow and flower best in full sun. To extend the flowering season throughout the summer, plant the corms at 7- to 10-day intervals until 2 months before the first frost is expected. Plant the corms 3 to 6 inches deep, depending on size of corm. To keep the plants erect, they must be staked, or "mound up" additional soil around the plants when they reach a height of 12 inches.

Cannas - Plant the rhizomes 2 to 4 inches deep and 12 to 18 inches apart.  Plant in full sun. Dig up the rhizomes before first frost for planting again next spring.

Caladium - Caladiums are grown for their beautiful colored leaves. They provide beauty in full sun to heavy shade, depending on the species selected. Plant caladium tubers when the soil temperature is approximately 70 degrees Fahrenheit. Plant with the top of tuber even with the soil surface and 8 to 12 inches apart. In the fall, dig the plants just before the first frost, and allow the foliage to wither in a protected place. Remove the foliage once it is dry, and store the tubers over winter at 55 to 60 degrees Fahrenheit. To encourage a single, large stem with leaves, remove all eyes except one before planting.

Daylilies - Plant the tuberous roots of daylilies 0.5 to 1 inch deep and 2 to 2.5 feet apart. There are many colors and plant heights to accommodate any landscape situation. The early summer blooms may be extended for more than a month with proper variety selection. Divide the clumps every 3 to 5 years.

Cultural Tips

  • Provide plenty of phosphorus for the development of the underground storage organs.
  • Soil test to insure proper soil pH is obtained and adequate fertility provided.
  • The smaller the bulb, tuber, or corm, the more shallow it is planted and the closer together they are planted.

Methods of Planting

  • Bulbs may be planted individually by using a bulb planter to remove a core of soil and placing the bulb in the hole, or use a trowel to open a hole within the soil. Pull the trowel toward you to open the hole for placement of the bulb.
  • Prepare a bed to plant bulbs in quantity.
  • Plant bulbs two and one-half times deeper than their diameters.

To extend the blooming period, plant bulbs at different depths. Location, such as sun versus shade, is an excellent way to vary the time of bloom up to 2 weeks.


Except for the daylilies you will need to dig up these plants after frost has browned the foliage. Then allow them to dry for about a week in a shady, well-ventilated site such as a garage or tool shed. Remove any excess soil and pack them in peat moss. Make sure the bulbs do not touch so that if one decays, the rot doesn't spread to its neighbors. Dusting them with fungicide before storage will help prevent them from rotting.

Caladium should be stored between 50 and 60 degrees F. But the rest of the bulbs mentioned should be stored near 40 degrees F. Finding a good spot may be difficult. Some people place them against a basement wall furthest from the furnace and insulate them so that the wall keeps them cool.

Kansas State University Research and Extension
Mississippi State University Extension




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