Northern gardeners need not give up on geraniums once the growing season reaches a close. They are sold as annuals where there are hard freezes and winters, but can be "overwintered" indoors and brought outside the next year to once again serve as reliable landscape additions, standouts in pots and as the focal point for porches, decks and other sunny places. Their flowers can range from hot pink to orange, and some are also cultivated for their scents. Protecting these Mediterranean natives from the cold they detest is a simple, money-saving move.
Containers can be used to overwinter geraniums, according to Iowa State University Extension. This step is easy for geraniums grown in pots outdoors, but care should be taken to not bring unwanted pests inside, the University of Minnesota Extension states. Plants can be dug up and replanted in pots with soil specifically for container growing. When inside, they should be set in a cool place that receives lots of direct sunlight, like near a north-facing window. Flourescent lights can also be used.
Once inside, some maintenance is required. They should be watered after potting, and watered whenever soil begins to dry. To promote strong growth, shoot tips should be pinched off once or twice, before plants return outdoors. A light fertilizer can be applied in the spring while plants are still inside, explains Iowa State University Extension.
Another overwintering option is taking cuttings from outdoor plants. Geranium cuttings root well, and the practice offers gardeners the ability to multiply their collection without buying more plants. A sharp knife should be used to remove a 3- to 4-inch stem tip, lower leaves should be torn off and the cut end of the stem dipped in root hormone. Cuttings can then be placed in a medium that promotes prolific root growth, like course sand, North Dakota State University Extension explains. Several cuttings can be grown in containers, and do best in a greenhouse climate that can be achieved with plastic bags over pots. Transplantation to other pots can occur once cutting roots are about 1-inch long, and the same care taken as for whole transplanted plants.
A third overwintering option involves forced dormancy without soil. Entire plants can be dug up before the first frost, shaken to remove soil from the roots, and placed in paper bags or hung upside down in a cool, dark place that is ideally 45 to 50 degrees Fahrenheit, says Iowa State University Extension. Two or three times during the winter, roots should be soaked in water for one to two hours. University of Minnesota Extension says plants with stems that don't remain firm and green should be discarded, but leaves can be expected to turn brown and fall off. Plants can be potted in late winter or early spring to help them break dormancy.
Plants should be planted outdoors after the danger of frost as passed. Sometimes, over potted overwintered plants will grow larger that those bought at stores in the spring, and bloom earlier.