Issue: October 25, 2008

Overwintering trailing geranium

Question:

I have a trailing geranium in a hanging basket that has large, beautiful flowers. I want to save this through the winter if possible. What shall I do to carry it through the winter? If it dies, then I will just buy a new one next year like I always do, but this is so pretty I would like to keep it.

Mary Alice S.
Albuquerque

Answer:

Geraniums are one of the plants that can often be carried safely through the winter, but the trailing form is more difficult than the more succulent (thick stems full of moisture) types of geranium.

For now, take it indoors (or into the garage) when there is danger of frost and return it to a bright location after the day warms. This will keep it in the best condition possible for as long as possible. When you finally need to bring it indoors, it will have a better chance to survive if it has good stores of food reserves in its stems and roots. It is storing food now, and from your description of how well it is flowering, it is in a location that is helping it grow and store those food reserves.

As the weather gets colder, you may need to keep it indoors more. The best indoor location for it will be a cool room (40 to 60 degrees at night) that receives south or east light. Put sheer curtains in the window to diffuse the light and slightly reduce the intensity of the light. During the day, keep the room as cool as possible, but at night allow it to get quite cool (as low as 40 degrees), and you will help your plant maintain its food reserves. Warm temperatures cause it to use the stored food more rapidly. Watch carefully for insect attacks as well. The indoor environment lacks the natural predators that help control harmful insects when your plants are outside. You need to identify problems early so that you can intervene and preserve the health of your plants. Many insects and damaging arthropods (spider mites and aphids) can be managed by putting the plant into the bath tub or sink and gently washing the insects from the plant with a stream of water. Other pests may require use of insecticidal soaps (also best applied in the bath tub) or manual removal with a cotton swab soaked in horticultural oil.

On warm days in the winter you can return the geranium outdoors to a bright, but shady location. Direct sunlight will burn the leaves after it has been indoors in reduced light. Watch the plant carefully to be sure it does not dry out. On warm winter days, it will use water more quickly than on the cooler days in the house. If the geranium continues growing and otherwise exhibiting good health (leaf color, flower production), you can give it a flowering houseplant fertilizer with some irrigations. This will further increase the storage of food reserves and help maintain the health of the plant. However, if the plant seems to become dormant, flowering ceases, and growth slows, fertilizer may cause it to decline further. In that instance, provide only water and if possible increase the light it receives each day or reduce temperatures by putting it in a cooler room.

In the spring as growth resumes and you are approaching the time that you will return it to its outdoor home, remove the plant from the pot, gently tease or wash soil away from the roots and replace the soil with new potting soil.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

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