Had an email from a reader the other day requesting help with her geraniums. Louise Hamilton-Delaney wrote: “I am wondering how one should care for geraniums during the winter months. I was given three of them in the spring and I left them outdoors until the middle of November at which time they were blooming for the second time. This second set of blooms was absolutely gorgeous and far exceeded in abundance the first blooms back in the late spring/early summer. I have been told by some to keep them in a darkened area during the winter months with very little watering, and I have also been told to treat them as you would any other plant during its non-blooming season. Since these were such a pretty addition to my small deck this year I would like to ensure their well being over the winter months. Any direction you could give me would be most appreciated.”
Actually both suggestions were correct, Louise ... with some modifications on the former recommendation. If you’re going to store geraniums in a dark room for the winter, you should dig them in the fall, shake all the soil from the roots and hang the plants upside down in a cool (45-50°F), dry place. About once a month soak the roots in water for a few hours. Most of the leaves will fall off during the winter but the stems should remain firm. In late February or early March cut back the geraniums to 1/3 their original height and pot them.
My preference for overwintering geraniums is to keep the original potted plants going. If they’re in large pots, repot each into a 6”-8” container and prune back to a third of their height. Water well and place in a bright, sunny window. The plants may still produce the occasional bloom, but this should be viewed as a resting period for them. They are fine growing in cooler temperatures. In early spring you can start adding water soluble fertilizer at half strength. Occasionally pinch or prune them to maintain stocky, well-branched plants.
Lastly, you have the option of taking cuttings from the original plants instead of overwintering the mother stock. Using a sharp knife or pruners, take 3” to 4” inch cuttings from terminal shoots. Pinch off the lower leaves, then dip the base of the cuttings in a rooting hormone. Stick the cuttings in a rooting medium of vermiculite, coarse sand, or a mixture of coarse sand and sphagnum moss.
Insert the cuttings into the mix so they stand up straight and then firm about the base of each. After all the cuttings are inserted, water them. To prevent wilting, place a clear plastic bag over the container. Place the cuttings in bright light, but not direct sunlight. Rooting should occur in six to eight weeks. Transplant into small pots and begin fertilizing at half strength a few weeks after planting.