How-To: Overwintering Geraniums
With fall around the corner, we're making plans for our plants during the cooler seasons. Along with pruning, mulching, and planting bulbs in preparation for spring, we're getting ready to overwinter some of our plants indoors. At the top of our list are colorful, annual geraniums, so we asked one of our garden experts-- plant buyer Karen C.-- for a few tips on overwintering these summer garden favorites. Karen says, "There are many types of geraniums. The perennial varieties are properly known as Geraniums, and can be left in the garden for the winter. Annual geraniums are technically Pelargoniums, and include five types: zonal (cutting), ivy, scented, seed, and Regal (also known as Martha Washington). All annual varieties except the Regals can be overwintered indoors, and there are three ways to do so; Regal types are more picky and don't overwinter well." Read on for Karen's tips.
Bareroot: If you have a cool, humid basement, you can store annual geraniums (except Regals) bareroot or dormant. Dig up the plants before fall's first frost and trim the branches back about halfway. Remove as much dirt as possible from the roots (carefully, as they are brittle), then either hang up the plants or place them in individual paper bags, left open for ventilation. The plants should be checked once a month or so and misted if they appear to be dry. If they are getting very dry and shriveled, they can be soaked for a few hours, then drained and put back into their bags. In spring, soak the geraniums overnight before planting. It might take a few weeks for new growth to appear; you can pot the plants indoors before the last frost to get a jump on growth for the new season.
Cutting: Over the winter, you can sprout new geraniums via cuttings. Snip the last 3-4" inches of a branch, removing the leaves from the lower half. Dip the cut end into a rooting hormone and place the branch about 1-2” deep into loose, well-drained potting medium. Place the cuttings in bright, indirect sunlight and keep the soil moist. Roots should develop in 3-4 weeks, at which point the new plants can be potted; be sure to water them well when potting. Afterward, place them in a cool, bright location and water only when the soil appears dry.
Around the House: Geraniums are fine houseplants, as long as they’re kept somewhere cool and bright. They should be dug up from the garden and potted before the first frost, and treated for insects or other diseases before being brought inside. Once inside, they're easy to care for; geraniums prefer minimal watering throughout the winter.
Karen adds, "Any overwintered geraniums will take a few weeks in the spring to adjust to their new outdoor conditions. As winter ends, they can be trimmed back to encourage new growth."
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My dad used to tell me that my grandmother would hang her geraniums upside in the basement during the winter. I've yet to try it!