What’s so great about geraniums? Well, if you took cheerfulness, contentment and good old-fashioned stability, and made a flower out of them, geraniums would be it. They’ve been around since great-grandma’s day and continue to be a staple in outdoor planters, containers and flowerbeds.
Geraniums are one of our favorite flowers, and each year Mary and I grow about 200 of them, enjoy them outdoors for the summer, and then bring them indoors for the winter. It isn’t difficult, and some gardeners use different methods, but here’s what’s worked well for us for many years:
- Before fall frost, dig up geraniums from flowerbeds or remove from outdoor planters.
- Pot into fresh top-quality soil like Miracle Gro Potting Mix into individual pots 4 or 6 inches in diameter. Geraniums grow best indoors if there’s one plant per pot, instead of multiples in a large pot.
- Geraniums like to become “pot-bound” so don’t use large pots indoors.
- Geraniums can become quite large over summer. Instead of trying to overwinter large geraniums, I prefer to cut them back to 4 inches above soil level. This usually removes most of the tops, leaving only stems and a few lower leaves. The plants quickly sprout new healthy, compact growth, and I can get more plants in a limited space. If you want to pot up and maintain geraniums in their current large size, that’s fine, but at some point they need cutting back, or they become woody and leggy. I’m aiming to produce compact, well-branched plants in 4 or 6 inch pots, similar to what we’d buy at a greenhouse in spring.
- Place in very sunny window. During winter’s short days, geraniums need all the direct sun they can get within a south, east or west window.
- If a large sunny window is lacking, geraniums grow very well under fluorescent lights. We grow 90% of ours in the basement under lights that are on automatic timers set for a length of 16 hours. Plain fluorescent tubes are fine, preferably a 2-tube shop light with one warm and one cool white tube. Locate plants so the lights are within an inch or two of the geranium tops.
- Fertilize once a month with a Miracle Gro type of fertilizer.
- Allow to dry out very well between waterings. If a finger inserted to the first joint feels moisture at the fingertip, don’t water. If in doubt, don’t water; wait a day and then check again. Keeping geraniums continually moist is certain death, especially if light is less than full sun.
- If plants weren’t cut back severely when brought indoors, they should be cut back on March 1 to 4-6 inches above soil level. They’ll branch beautifully and will be full and bushy for planting outdoors in May.
Keeping Geraniums growing in this method is the most certain way of overwintering success. Over the years, other methods have been used that work for some gardeners, and not for others, depending on individual conditions. These methods include hanging the geraniums upside down in root cellars, placing pot-and-all in a cool basement window, and enclosing in brown paper bags.
The same geranium plants can be grown outdoors, cut back and brought indoors for the winter, and returned outdoors in a cycle for several growing seasons. One gardener has been using the same geraniums for over 30 years, which I think is a record. I like to start some fresh geranium cuttings each fall from the parts I cut back. In that way, we’ve got some newer plants to replenish those that get older and more woody.
If I could summarize the 3 most important aspects of keeping geraniums over winter, they would be (1) plenty of light (2) repotting into the correct size pot in good soil mix and (3) the benefits of drastically cutting back to encourage fresh, vigorous growth instead of old, woody stems.