Extension News

Ask the ISU Experts

Note to media editors:

Got gardening questions? Contact the Hortline at (515) 294-3108 (Monday-Friday; 10 a.m. - 12 noon and 1 - 4:30 p.m.) or send an e-mail to hortline@iastate.edu. For more gardening information visit us at Yard and Garden Online at www.yardandgarden.extension.iastate.edu


How do I over-winter calla lilies indoors? 

Calla lilies (Zantedeschia spp.) are tender perennials. Their rhizomes must be dug up in the fall and stored indoors over the winter months. After a killing frost, cut off the foliage 1 to 2 inches above the soil surface. Carefully dig up the rhizomes. Do not cut or injure the rhizomes. Dry the rhizomes in a warm, dry location for one to two weeks. After drying, bury the rhizomes in vermiculite, sawdust or peat moss and store them in a cool (50 to 60 degrees F), dry location.


I would like to grow bittersweet and use the colorful fruit in dried flower arrangements. What are its cultural requirements? 

American bittersweet (Celastrus scandens) is a fast growing, twining, native vine. It will often grow 20 to 30 feet long with adequate support. American bittersweet is dioecious. Dioecious plants produce male and female flowers on separate plants. Small, inconspicuous, yellowish white flowers are produced on male and female plants in spring. When properly pollinated, female plants produce three-lobed fruit (capsules) after flowering. The mature capsules split apart in early fall exposing the decorative, crimson-colored seeds. While only female plants produce fruit, a male plant must be present for pollination and fruit set. 


Bittersweet is easy to grow. It tolerates dry sites and poor soils. Best fruiting occurs when plants are grown in full sun on a fence or other support. Plants sold at garden centers or through mail-order catalogs are usually not labeled as male or female. As a result, it’s best to plant at least three or four bittersweet vines to insure getting one or two female plants. Gardeners should be patient. Female plants may not fruit for several years. 


I planted a Martha Washington geranium outdoors in spring. Unfortunately, it didn’t bloom all summer. Why? 

Martha Washington or regal geraniums (Pelargonium x domesticum) produce beautiful flowers. Unfortunately, cool (50 to 60 degrees F), night temperatures are required for flower formation. Few flowers form during our summer months because nighttime temperatures are usually too high. The common garden geranium (Pelargonium x hortorum) and ivy geranium (Pelargonium peltatum) are more heat tolerant and better choices for Iowa gardens. 



Contacts :

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

Jean McGuire,Extension Communications and Marketing Services, (515) 294-7033, jmcguire@iastate.edu