Growing Together: How to keep geraniums from year to year

Don Kinzler
Forum News Service

If you could take a sunny disposition, contentment, and good old-fashioned reliability and create a flower, it would be the geranium. They’ve been gracing our homes since pioneer days and are an ever-popular staple in outdoor pots, planters and flower beds. Geraniums are also the most popular plant for bringing indoors in fall and keeping over winter so they can go outside again next spring.

There are different ways to keep geraniums from year to year. Some gardeners move their potted geraniums to a cool spot in the basement, where they remain partially dormant during winter with minimal watering, and are brought back into active growth in spring. A few people follow the old-time practice of storing geraniums bare-root in a root cellar-type atmosphere. Several well-experienced gardeners have told me their geraniums have cycled outdoors and indoors for over 30 years.

My wife, Mary, and I bring 100 geranium plants or cuttings indoors each fall to keep for next spring’s outdoor containers. It doesn’t require as much room as it sounds, using a successful method that saves space, rejuvenates older plants and is easy.

Here’s the recipe for wintering a quantity of geraniums that will rival greenhouse-quality plants by next spring:

  • Before they’re injured by fall frost, remove geraniums from outdoor planters or flower beds by gently digging or lifting out the plant and its roots.
  • Geraniums often become large over summer. Instead of trying to overwinter large geraniums, I prefer to cut each plant back to 3 inches above soil level. This removes most of the tops, leaving only stems and a few lower leaves. More plants fit in a limited space, and they quickly sprout new healthy, compact growth.
  • The goal is to produce compact, well-branched plants in 4- or 5-inch pots, similar to what we’d buy at a greenhouse in spring.
  • Pot the pruned geraniums into individual 4- or 5-inch diameter pots using top-quality soil like Miracle-Gro Potting Mix, or a mix recommended by your locally owned garden center. Geraniums grow best indoors if there’s one plant per pot, instead of multiples in a large pot.
  • Geraniums enjoy being “pot-bound” so don’t use large pots indoors.
  • Place in a window where the plants will receive direct sunshine. South windows are best, followed by east and west.
  • If a large, sunny window is lacking, geraniums grow very well under fluorescent or LED lights, with automatic timers set for 16 hours on and 8 hours off. We grow ours in a corner of the basement under shop-type fluorescent hanging fixtures containing one warm and one cool tube. Locate plants so the lights are within an inch or two of the geranium tops.
  • Fertilize once a month with a water-soluble fertilizer.
  • Allow the geranium soil to dry out very well between waterings. If a finger inserted to the first joint feels any moisture at the fingertip, don’t water. If in doubt, wait a day and then check again. Geraniums easily rot if kept too moist. If in question, err on the dry side.
  • Continue to grow the plants during winter as you would houseplants, enjoying the blossoms that arise by midwinter. About March 1, pinch back any winter growth that became spindly, and remove blossoms and flower buds. Begin water-soluble fertilizer every two weeks. The geraniums will branch beautifully and will be in prime conditions for planting outdoors in May.

Besides overwintering the original plants, I like to start some fresh geranium cuttings each fall from the tips of plants I cut back. When rooted, they provide new plants to replenish any that are old and woody. Geranium cuttings, about 3 inches long, produce roots in two to three weeks in a mixture of half sand, half peat moss. When roots are about 2 inches long, plant into potting mix in 4-inch diameter pots, and grow as directed above.

Fielding questions

Question: This plant is spreading on the west side of my house. Can you identify it, and what can I do about it? — Martin Ness.

Answer: The weed in your photograph is creeping Charlie, sometimes called ground ivy. Early settlers brought this non-native plant to North America from Europe, as they felt it would make a hardy groundcover. And that it is. Unfortunately, it escaped cultivation long ago, and is now one of the most tenacious weeds in the lawn and landscape.

Creeping Charlie is a winter-hardy perennial, spreading by creeping stems that root as they crawl. Blue-lavender flowers produce seed, making a second source of spreading. In lawns, the low-growing plant habit hugs the ground, escaping the lawn mower.

Fall is the most effective time to control hard-to-kill weeds like creeping Charlie, and an effective active ingredient is the herbicide triclopyr, which can be found on the label by examining products at the garden center. Apply triclopyr spray in September after the first light frost. This fall application is very important, as weeds are moving material, including the weed killers, down into their roots for winter storage.

Repeat application next May or June when creeping Charlie is producing blue flowers. Triclopyr is a broadleaf weed killer, killing broadleaf plants but not harming lawngrass. In landscapes and flower beds, herbicides must be spot-applied, as chemicals that kill creeping Charlie will also kill broadleaf perennials, trees and shrubs.

Always follow the directions on the label. Triclopyr can cause damage to trees, because it can move downward in the soil and enter roots, so should not be applied over the rootzone of trees or shrubs.

Control by digging is difficult, yet might be the only solution in perennial flowers or landscapes. Care must be taken to remove every sprig of Charlie’s stems. Alternatively, perennial flowers can be dug out in early spring or fall, set aside in pots, and creeping Charlie treated with herbicide.

Q: I feel it’s too late to be trimming yews and other evergreens. Am I correct, and when is the proper time? — Marlys C.

A: Yes, it’s generally better not to trim evergreen in the fall, as it can open them up to greater winter injury. Generally, all evergreens are best pruned in May and June, about the time their new growth is emerging or expanding. Of evergreen types, arborvitae are a little more flexible about timing of pruning, because they continue growing throughout the summer.

Q: I have a question about pumpkins. I was cutting pumpkin vines in my corn patch that I thought didn’t have fruit, when I cut off the main vine of a large pumpkin. It had just started to turn orange. Do I leave it in the garden or bring it in? Will it still ripen? — Brenda.

A: If pumpkins are showing a little bit of orange, they’ll usually progress to full color, if given warmth and light. If outdoor daytime temperatures will be close to the 70s, it’s fine to leave the pumpkins in the garden, exposed to sunshine.

If weather conditions don’t cooperate, pumpkins can be moved to a sunny, warm location, such as a south-facing porch. Occasionally rotating them toward the sunlight will promote uniform orange color.

Pumpkins can tolerate light frosts fine, but temperatures between 25 and 28 degrees or lower can make them soft and water-soaked, especially if they haven’t developed a hard shell yet. If additional hard freezes are forecast, moving the pumpkins into the garage on cold nights and back to their warm, sunny spot during the day will keep their color progressing to bright orange in time for Halloween.

Geraniums are a favorite flower for keeping from year to year.
Geraniums can become quite large during the summer. Cutting back produces a fresh new plant.
Potted into 4- or 5-inch pots, geraniums grow beautifully during winter in a sunny window or under fluorescent or LED lights.
A reader wonders what can be done to get this weed, known as creeping Charlie, under control.