Don Kinzler, Published October 18 2013
Growing Together: Brighten winter by moving your plants indoors
Maybe you took new cuttings in September that have now rooted, or perhaps you’d like to keep the geraniums from outdoor planters. Saving a few dollars next spring might be your motivation, or maybe you don’t like to see plants die without just cause.
Rooted geranium cuttings should now be potted into 4- or 5-inch pots using a good mix like Miracle Gro Potting Mix. If the pots are too large, the cuttings are more prone to overwatering and root rot.
Geraniums that have grown outdoors all summer in planters or flower beds can be dug up and brought indoors. There are two choices: you can grow them as houseplants, or you can preserve them during winter by letting them go dormant (keep reading for instructions on this technique).
To maintain this summer’s geraniums as blooming houseplants, dig them up and cut back the stems to 3 or 4 inches above soil level. This will seem drastic and traumatic if you’ve never tried it. But we need to rejuvenate them by forcing fresh new growth from the lower stems.
When you cut them back, there may be only a few leaves and mostly bare stems. Clean away dead, dry leaves. Pot the plants, and within several weeks new sprouts should appear along the stems.
Proper light is the No. 1 requirement for growing geraniums indoors. A south-facing window receiving full winter sunshine is best. Plants should be located directly in front of the window as close to the glass as possible where the leaves will actually be bathed in sunlight rather than just bright light. East and west windows are next best.
If you do not have a sunny window, geraniums grow beautifully under fluorescent lights.
“Grow lights” specially made for this purpose work well, but research from the universities of Alaska and Vermont have shown ordinary fluorescent lights perform equally as well.
I’ve had great success with regular fluorescent tubes in shop-type light fixtures. Combining “cool white” and “warm white” tubes in a double fixture is often recommended. Sometimes I can’t find the warm white type, so I’ve used all cool white with success.
Plants should be located under the lights within 3 to 6 inches of the tubes. Lights will need to be raised as the plants grow, which is easy if the fixtures are hung on chains. Or you can raise or lower the plants themselves by placing something underneath the pots.
Geraniums should receive 14 to 16 hours of light each day. A light timer works well. Rotate plants under the lights for even growth.
Whether geraniums are grown in windows or under lights, they prefer to be kept on the dry side. Wet the soil thoroughly when you water, but allow to dry between watering. It is better to err on the dry side with geraniums. About once a month add soluble fertilizer to the regular watering.
Geraniums are capable of going dormant, being stored over winter and then started back into growth next spring.
Temperatures must be very cool, a constant 35 to 40 degrees. An unheated part of the basement, a three-season porch or some garages might work. The plants must not freeze.
After you’ve dug the plants and brought them indoors, cut the tops back by half. You should pot them, moisten the soil just a little and cover the pot with an overturned paper bag. Leaves will dry and wither. Check the plants every two weeks and spray a little water on the stems and the soil around the roots.
You can also store the plants “bare root.” Shake off excess soil after digging, cut the tops back by half and place the plants in paper bags with the tops loosely folded over. You can store several plants per bag. Every two weeks spray a little water on the stems and roots.
Next March cut the tops back to firm green stems, pot and place in a sunny window or under lights. Success rate with dormant geranium storage is about 50-50.
More outdoor flowers as houseplants
If you hate to see the growing season end, it can be extended by bringing in coleus, begonias, mandevilla, sweet potato vine, bacopa snowstorm, gerbera daisy and many ivies.
Trim them back a little and repot. Most of these plants need as much winter sun as possible from a south window or artificial lights.
Winter won’t seem as long when our homes are filled with the same blooming plants we enjoy outdoors.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at firstname.lastname@example.org