This is a good article. These methods can be applied to other plants, also.
Yard and Garden: Properly Overwintering Geraniums
As fall arrives and the leaves begin to change, we are reminded that it won’t be long until the first frost hits and winter arrives. We all have outdoor plants, but many of us wonder about the best way to treat them to survive winter. How should you handle your geraniums to make sure they last through winter to thrive next spring?
Here are some tips from Iowa State University Extension and Outreach horticulturists on overwintering geraniums. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or firstname.lastname@example.org. [ Johnson County Hortline 319-337-2145]
How can I overwinter geraniums indoors?
Geraniums can be overwintered indoors by potting up individual plants, taking cuttings or storing bare-root plants in a cool, dry location. Remove plants from the garden (or take cuttings) prior to the first fall frost.
How do you overwinter geraniums as potted plants?
Before the first fall frost, carefully dig up plants growing in the ground and place in large containers. Water each plant thoroughly. Plants growing in containers can simply be brought indoors. Place the geraniums in a sunny window or under artificial lighting. Geraniums prefer cool indoor temperatures.
Daytime temperatures of 65 to 70 degrees Fahrenheit and slightly cooler night temperatures are ideal. During their stay indoors, water plants when the potting soil becomes dry. Geraniums are likely to become tall and lanky by late winter. In March, prune back the plants. Cut back the geraniums by one-half to two-thirds. The geraniums will begin to grow again within a few days and should develop into nice specimens by May.
How do I take geranium cuttings?
Using a sharp knife, take three- to five-inch stem cuttings from the terminal ends of the shoots. Pinch off the lower leaves, then dip the base of each cutting in a rooting hormone. Stick the cuttings into a rooting medium of vermiculite or a mixture of perlite and sphagnum peat moss. Pots and flats with drainage holes in the bottom are suitable rooting containers.
Insert the cuttings into the medium just far enough to be self-supporting. After all the cuttings are inserted, water the rooting medium. Allow the medium to drain for a few minutes, then place a clear plastic bag or dome over the cuttings to prevent the foliage from wilting. Finally, place the cuttings in bright light, but not direct sunlight. The cuttings should root in six to eight weeks. When the cuttings have good root systems, remove them from the rooting medium and plant each rooted cutting in its own container. Place the potted plants in a sunny window or under artificial lighting until spring.
How do you overwinter geraniums as bare-root plants?
Carefully dig up the geraniums before the first fall frost. Shake the soil from the plant’s roots. Then place one or two plants in a large paper sack and store in a cool (45 to 55 degree Fahrenheit), dry location. An unheated bedroom or indoor porch might be a suitable location.
An alternate method is to hang the plants upside down in a cool, dry location. The foliage and the shoot tips will eventually die. In March, prune or cut back each plant. Remove all shriveled, dead material. Prune back to firm, green, live stem tissue. After pruning, pot up the plants and water thoroughly. Place the potted geraniums in a sunny window or under artificial lighting. Geraniums that are pruned and potted in March should develop into nice looking plants that can be planted outdoors in May.