Extension News

Ask the ISU Garden Experts: Hackberries, Redbuds, and Drought-Tolerant Annuals

Note to media editors: Got gardening questions? Call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or e-mail us at hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu

5/14/2009

Why is my hackberry tree losing some of its new leaves?

The loss of leaves on hackberries in spring is an occasional phenomenon in Iowa and surrounding states. The exact cause has never been determined. In past years, no association was found between the leaf drop and insects or diseases. The most popular theory is that cold spring temperatures may have damaged the leaf buds or newly developing leaves, causing the leaf drop. It’s likely the loss of leaves in spring is temporary. In past years, affected hackberries quickly developed new leaves and recovered completely.

My five-year-old redbud tree is not leafing out this spring. What happened to it?

The redbud tree may have been severely damaged or destroyed by very cold temperatures this past winter.

The redbud (Cercis canadensis) is native to much of the eastern United States, including southern Iowa. It is widely planted in central and southern Iowa. Redbuds are usually grown from seeds. The hardiness of seed-grown redbuds varies somewhat based on the source of the seeds. Plants grown from seeds collected in Iowa and other northern seed sources are generally hardy to minus 25 to minus 30 F. Redbuds grown from southern seed sources are less hardy.

When purchasing a redbud, be sure to select one that was grown from a northern seed source. Redbuds perform best in moist, well-drained soils in partial shade to full sun. Whenever possible, select a sheltered location in central and northern Iowa.

What are some good drought tolerant annuals?

Many annual flowers perform best when they have a consistent supply of moisture throughout the growing season. However, some annuals tolerate dry conditions quite well. After they’ve been planted, drought tolerant annuals often need to be watered a few times until they’re established. Once established, drought tolerant annuals require little watering. Drought tolerant annuals include periwinkle (Catharanthus roseus), cockscomb (Celosia spp.), spider flower (Cleome hassleriana), cosmos (Cosmos spp.), globe amaranth (Gomphrena globosa), medallion flower (Melampodium paludosum), rose moss (Portulaca grandiflora), dusty miller (Senecio cineraria), dahlberg daisy (Thymophylla tenuiloba) and zinnia (Zinnia spp.).

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Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu 

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu