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Using summer-flowering bulbs in the landscape

Published February 16, 2012

Using summer-flowering bulbs will add that extra spot of color in the home landscape at a time when spring- flowering shrubs and bulbs have been done for a while, said University of Illinois Extension horticulture educator Richard Hentschel.

"Summer bulbs will provide different textures, plant shapes, and flower colors to the landscape," he said. Gardening catalogs and the Internet offer a great many summer bulbs to choose from. Some of the more popular are canna, gladiola, calla lily, elephant ear, dahlia, and agapanthus. Some are true bulbs, others are corms and tubers. The main difference between spring and summer bulbs is the ability to survive winter weather. Spring bulbs go dormant in the fall and the bulbs, corms, and tubers survive in the soil in temperatures below freezing. Summer bulbs are more tender and cannot tolerate below-freezing temperatures. They flower well after spring bulbs are done.

Summer bulbs are planted once the soils warm and well after the last spring frost. Cannas and elephant ear need warm soil temperatures. If it is warm enough for tomatoes to be set out, you can plant summer bulbs.

"If you own a soil thermometer, check to make sure the soil is at 60 degrees F or higher," Hentschel said. "Most bulbs will prefer a well-drained soil, so be generous with the compost. You can even create a bit of a raised bed, further ensuring good soil drainage."

Drier soil is also warmer soil. Compost provides nutrients and creates water and air spaces that increase both water holding and drainage at the same time. The continued success of any bulb will be the ability to store the reserves it needs to grow and bloom in the next season.

Gardeners who like to get a head start can begin to grow summer bulbs indoors, starting one to two months before it is time to transplant them outdoors. The summer bulb already has everything inside to grow, including the flower buds. Start with clean containers and a fresh soil mix.

"It will be better to start a little later rather than earlier if you are not sure of your planting date outdoors," said Hentschel. "Planting the bulbs directly in your flower beds is just like planting your spring-flowering bulbs. Unless your instructions state something different, bulbs usually are planted at depths of two to three times their diameter in the soil."

"Any bulbs you have grown ahead would be planted to the same depth as the container because the bulbs have already established themselves. Bulbs grown in larger containers can be used on the deck, patio, or near the front door for added color," he continued.

Spring bulbs, corms and tubers will certainly add to the landscape and also to your fall gardening activities.

"Your summer bulbs will need to be dug up after the frosty weather has taken the foliage down and before the soil freezes," he added. "Allow them to dry down and store in a cool area, above freezing but not too warm or they will begin to grow. "