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Wednesday, Oct. 17, 2007 08:53 am

Overwintering geraniums

Gardeners have several alternatives to save the flowers for next year

Untitled Document Sad at the thought that your cheery geraniums will soon fall victim to the dropping temperatures of autumn? It’s possible to beat the frost and save the plants by taking them inside for the winter.
“As soon as we get freezing temperatures, most unprotected annual geraniums will turn a mushy green and die,” says David Robson, a horticulture educator with the University of Illinois Extension. “However, it’s possible to take those geraniums before they get nipped by a hard frost and overwinter them indoors. Gardeners have several alternatives, including potting the plants, taking cuttings from them, or storing the plants as bare-root specimens. It is important to make sure that the plants are vigorous, healthy, and insect- and disease-free. White flies, aphids, and mealybugs, which hide on the plants, will spread indoors, where predators can’t keep them in check. “Check the soil to avoid bringing in other hitchhikers,” Robson says. “Some gardeners will always repot the geranium in fresh houseplant soil. That might be a little unnecessary, though it practically guarantees no soilborne insects are brought indoors.”
For plants in larger pots or in the ground, carefully dig up the geranium and plant it in a 6- or 8-inch pot. Use potting soil instead of garden soil to avoid a soggy, heavy soil indoors. Prune back each plant by half. Geraniums require at least 10 to 12 hours of light and temperatures of 65 to 70 degrees during the day and 55 to 60 degrees at night. Excessively warm temperatures tend to encourage legginess. The cutting approach permits the use of smaller plants that take up less space and have a better chance of acclimating to indoor light, temperature, and humidity levels. “Take 4 to 6 inches of terminal growth and strip off the bottom 2 or 3 inches of leaves,” Robson says. “Dip each cutting in a rooting hormone. Stick the cuttings in sand, perlite, or vermiculite up to the first set of leaves. Water thoroughly and place in a bright, sunny window or under fluorescent lights. Cuttings should root in one or two months. When rooted, pot in a 3- or 4-inch pot and continue to grow until spring.”
The bare-root approach is by far the easiest but also the least successful, Robson says. It involves digging up your geraniums, shaking most of the soil from the roots, and hanging the plants upside down in a cool basement or dry crawl space where the temperature hovers at 45 to 50 degrees. “Once a month, soak the roots for an hour or two in warm water,” he says. “Expect that leaves will probably turn brown, dry up, and fall off. If all goes well, though, stems should remain green.
“In March, cut each plant back by half or to green, fleshy, solid stems. Pot each plant up and water thoroughly, placing the geraniums in a bright, sunny window. Plants should start budding out, sending out new shoots, and developing into attractive plants that can be set outside in May.”

For information about the University of Illinois Extension Sangamon-Menard Unit, go to www.extension.uiuc.edu/sangamon. 
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