Late summer is the time we start thinking about how to overwinter our favorite plants. September is the best month to start thinking about which plants to keep and which to let succumb to Jack Frost. Geraniums are one of those annuals that you can save from year to year.
However, they won’t bloom beautifully all winter long unless you have a greenhouse with plenty of light and space. Since most of us don’t there are a few options for saving geraniums over winter.
First, disinfect any tools and pots that you’ll be using to overwinter plants with one part bleach to nine parts water. Second, carefully examine the plant to be stored for disease and insects. Choose only healthy plants.
One method is to bring the entire pot into a frost-free environment. If the plant is in the ground, dig and repot the plant, if it’s already potted just bring it indoors. If you do this method, trim the plants back to at least half to compensate for the lower light conditions. If the plant loses lots of leaves indoors, it’s an indication that the plant isn’t receiving enough light to support the size of the plant.
Another method is to dig up the plant, knock the soil from the roots and hang the plant upside down in a cool moist basement with an 80 percent humidity and 35 to 45 degree temperature. This method requires an older unfinished basement. If you don’t have these ideal conditions, try storing the geraniums in a covered cardboard box alongside an open can of water to provide humidity. Try this method in a heated finished basement or even in a heated garage, making sure to keep water in the can. In early spring the geranium will have lost all of his leaves, will have a green stem and may even be startling to sprout. Soak the roots in water for 24 hours and plant it after cutting off the dried branches. Don’t set this plant in bright direct sun right away because the plant could sunburn and not survive.
A third method is to take cuttings from the mature plant, remove the lower leaves, dip the stem in rooting compound, and plant in a soilless potting soil. Cover the entire pot with a plastic bag to form a miniature green house. Place the pot in bright light but not direct sunlight. When the plant has rooted usually three to four weeks repot into another pot with potting soil and keep in a sunny place. If the plant gets long and leggy, trim it back.
In spring, once temperatures warm, harden off the plants by moving them outside in the shade for a couple of hours every day increasing the time and the amount of light each day for about two weeks. At that point your geranium will be ready for its new summer location.
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For questions about seeds and other gardening issues, call the Linn County Extension Hortline at (319) 447-0647 from 10 a.m. to noon weekdays.