Geraniums (Pelargoniums) are technically perennial plants that thrive in warm climates but will not survive winter outdoors in most regions. Overwintering them preserves your favorite varieties and ensures they return robustly the following spring. This process transitions the plant into a state of dormancy or reduced growth until the cold weather passes, allowing you to enjoy mature plants without buying new ones each year.
Preparing Geraniums for Dormancy
Preparation must begin before the first hard frost, as geraniums are sensitive to freezing temperatures. Inspect the entire plant thoroughly for signs of disease or pests, such as whiteflies or spider mites, before bringing them indoors. Discard any plant showing significant infection to prevent spread to other plants in storage or your home.
Next, prune the geraniums to reduce their size and conserve energy, cutting them back by approximately one-half to two-thirds of their height. Use sharp, clean pruners to remove all dead leaves, spent flowers, and any diseased or damaged stems. This concentrates the plant’s energy into the root system, promoting healthier growth in the spring.
If storing bare-root, carefully dig up the plants and shake off as much soil as possible. Let the roots dry on newspaper in a sheltered area for a few hours to prevent mold during storage. If overwintering in pots, ensure the container is clean and use fresh potting mix if transplanting from the ground.
Choosing a Winter Storage Method
The overwintering method depends on available space and the level of care desired. The main strategies are bare-root dormancy or keeping the plants actively growing as houseplants.
Bare-Root/Dormant Storage (Hanging)
The bare-root method places the plant into a true dormant state, requiring minimal space and attention. After digging up the plant and removing the soil, store it by placing one or two plants inside a large, open brown paper bag or cardboard box. Alternatively, hang the plants upside down from the rafters in a cool, dark location.
The storage area, such as a cool basement or unheated cellar, must remain reliably above freezing, with an ideal temperature range between 45 and 55 degrees Fahrenheit. This cool temperature slows the plant’s metabolism significantly, allowing it to rest until spring. The dryness of the storage area helps prevent fungal diseases and rot.
Potted/Active Storage
To keep geraniums partially active, treat them like houseplants by bringing the entire potted plant indoors. Before moving them inside, cut the plant back by about one-third. Place the pot in a location that receives bright, direct sunlight, such as a south-facing window. If natural light is insufficient, supplemental grow lights can be used to prevent the plants from becoming leggy.
The ideal indoor temperature is 60 to 65 degrees Fahrenheit during the day, with slightly cooler temperatures at night. This setup allows the plant to continue slow growth throughout the winter, though flowering will be minimal due to reduced light intensity.
Taking Cuttings
Taking stem cuttings in the fall is a space-saving alternative to overwintering the entire parent plant. Use a sharp, sterile knife to take three-to-four-inch cuttings from the tips of healthy shoots, cutting just below a leaf node. After removing the lower leaves, dipping the cut end in rooting hormone powder increases the rooting success rate.
Insert the cuttings into a well-draining rooting medium, such as perlite or a sand/peat moss mixture, in small pots. Place the pots in a bright location with indirect light and keep the medium consistently moist. Root development is encouraged within six to eight weeks, providing a fresh, compact start for next spring.
Essential Care During Winter Storage
Stored geraniums, whether dormant or active, require specific maintenance to survive the winter. For bare-root plants, the main concern is preventing the root system from completely drying out. Check the plants monthly for shriveled or overly dry stems.
If stems appear dry or wrinkled, briefly mist the plant or soak the roots in water for about an hour to rehydrate them. Allow the plant to dry completely before returning it to storage. Discard any plants with soft, mushy, or moldy stems, as they will not recover.
Potted geraniums require minimal watering, only when the top inch or two of the soil feels dry. Overwatering is the most common cause of failure for active storage, leading to root rot in soggy soil with limited light. Monitor for pests like whiteflies and spider mites, and use insecticidal soap if an infestation is found.
Reintroducing Plants in Spring
The transition back to active growth in late winter or early spring must be gradual to prevent shock. For bare-root plants, begin this process six to eight weeks before the last expected frost date. Remove the plants from storage and prune the stems back to firm, green tissue, discarding any dead or shriveled wood.
Soak the root ball in lukewarm water for a few hours to fully rehydrate the plant before potting it in fresh, sterile potting mix. Place the newly potted geraniums in a bright, warm location and water thoroughly to encourage new growth. For plants overwintered in pots, prune back any leggy growth developed over the winter.
Once the threat of frost has passed, the final step is hardening off the rejuvenated plants before permanent planting. Hardening off is a two-week process that gradually introduces the plants to outdoor conditions, including direct sun, wind, and cooler temperatures. Start by placing the plants in a protected, shaded spot outside for a couple of hours each day. Gradually increase the duration and intensity of their exposure over the next fourteen days. This slow acclimatization strengthens the plant, preparing it to thrive in the garden.