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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Overwintering Geraniums

This article was published originally on 9/17/2004

With the rainbow of flower and leaf colors, it is hard to watch beautiful and costly geraniums die from a hard frost. There are several ways to keep those geraniums through the winter for a head start on blooms next spring and a savings to your garden budget.

Keep them growing in containers

Geraniums grow easily indoors in containers with proper care and environmental conditions. Before the first frost, cut back plants to half of their original size and inspect them for signs of insects or disease. Then, dig up healthy plants and transplant into containers. Use a potting mix made for containerized plants instead of garden soil. Garden soil is often heavy, compacted, and drains poorly in containers. Place containerized plants in a cool location with plenty of bright, direct sunlight. Water plants well after potting and as needed when the soil begins to dry. Shoot tips may need pinching once or twice during the winter to promote branching and prevent weak growth. Before planting outside in May, fertilize lightly. Plants kept in containers over the winter are typically larger than most geraniums sold in the spring. This allows you to have a head start on growth and blooms for next year's garden.

Taking cuttings from outdoor plants

Geraniums root readily from cuttings. This is also a great way to multiply the number of plants for next year's garden. To take a cutting, remove a 3- to 4-inch section of the plant's stem tip with a sharp knife. Pinch off the leaves from the lower half of the cutting and dip the cut end into a rooting hormone. Rooting hormones are sold in powder or liquid form at your local garden center or discount store. Stick the cuttings in a moist, porous, well-drained rooting media such as coarse sand, perlite, or vermiculite. Cuttings can be rooted in individual pots or several cuttings can be placed per container. Make sure the container has holes for drainage. Ideally, cuttings root best in a moist, humid environment. This is easy to achieve by securing a clear plastic bag over the cuttings and container. This "mini-greenhouse" should be placed in bright, but indirect light. Check the media occasionally to insure it remains evenly moist. Rooting normally occurs in 6 to 8 weeks. After roots are approximately 1-inch long, transplant cuttings into a 3- to 4-inch container with a standard well-drained potting soil. Place in a sunny window and water as needed. Pinch shoot tips back to force branching and prevent spindly growth. New plants produced from cuttings should be vigorous and about the same size as most geraniums sold in spring.

Dormant Storage

Geraniums are unusual and unlike many annual flowers, they have the ability to survive for most of the winter without soil. If properly stored, they can resist extended dry periods due to their thick, succulent-like stems. To overwinter geraniums in dormant storage, dig up the entire plant before frost and gently shake the soil from the roots. Place the plants inside open paper bags or hang them upside-down from the rafters in a cool, dark location for the winter. Ideally the temperature should be between 45-50 F. Two or three times during the winter, take the plants out the bags or down from the rafters and soak the roots in water for 1 or 2 hours. At this time, inspect the stems. While many of the leaves will die and fall off, the stems should remain firm and solid. Discard any geraniums with shriveled stems, since those plants will most likely die. Pot up healthy dormant geraniums in containers in late March or early April. Water plants thoroughly and cut back the dead stem tips. Place potted plants in a sunny window to initiate new growth. It often takes several weeks for plants to initiate growth after dormant storage.

No matter how geraniums have been overwintered, they should be healthy, free-flowering plants for spring. After being indoors all winter, your geraniums may be as anxious as you are for spring planting. Plant them after the danger of frost has passed and enjoy their colorful blooms all summer. You can invest your savings in new geranium varieties to overwinter next year.



This article originally appeared in the 9/17/2004 issue.

Year of Publication: 
2004
Issue: 
IC-491(22) -- September 17, 2004