Geraniums, scientifically known as Pelargonium species, are widely cherished for their vibrant, continuous color throughout the warmer months. Though they are botanically tender perennials, they are commonly treated as annuals in regions with cold winters because they cannot survive a hard freeze. Rather than discarding these plants when temperatures drop, gardeners can employ several simple methods to preserve them over the cold season. Successful overwintering allows you to enjoy mature, robust plants the following spring, offering a significant head start on the gardening year.
Preparing Geraniums for Winter Storage
The process of preparing your geraniums must begin well before the first hard frost arrives, typically when night temperatures consistently fall below 40°F. Moving plants indoors after they have been exposed to freezing conditions can cause irreparable cellular damage. For plants growing directly in the ground, they must be carefully dug up and potted into a container with adequate drainage for transport indoors.
Before moving plants, thoroughly inspect them for pests like whiteflies or spider mites to prevent indoor infestations. Any diseased or damaged foliage and spent flowers should be removed to reduce the risk of mold or fungal issues during storage. A light pruning, cutting the plant back by about one-third to one-half, helps manage the plant’s size for its winter location and conserves energy.
Overwintering Method: Active Indoor Growth
The active indoor growth method treats the geranium like a houseplant, maintaining it in a semi-dormant state throughout the winter. This is the simplest choice for plants already in pots or for those who desire continuous, though reduced, foliage. The ideal location is a cool, brightly lit area, such as a sunny south-facing window or under supplemental grow lights.
Geraniums prefer cooler indoor temperatures, ideally between 60°F and 65°F during the day and slightly lower at night. Warm, dry air from heating vents should be avoided, as it can encourage leggy growth and attract spider mites. Watering must be reduced from the summer schedule; allow the top inch of soil to dry out completely between waterings to prevent the soil from becoming bone dry and discourage root rot.
Overwintering Method: Dormant Bare-Root Storage
The bare-root method forces the geranium into a state of true dormancy, which is highly effective for saving space and works well for plants with woody stems. This process begins by digging up the entire plant and gently shaking or rinsing off all the soil from the root system. The plant is then pruned severely, cutting the stems back to a length of about 6 to 8 inches to minimize moisture loss and conserve the plant’s energy.
The prepared plants must be stored in a cool, dark, and dry environment where the temperature remains consistently between 45°F and 50°F. A cool basement, dry cellar, or unheated garage that stays above freezing is often suitable. To store, the plants can be wrapped loosely in brown paper bags or newspaper, or hung upside down, which helps retain moisture in the root crowns.
During storage, the plants will naturally drop most leaves, but the stems should remain firm. Check them monthly for signs of shriveling or desiccation, especially in very dry conditions. If roots appear shriveled, a brief soak in water for one to two hours can rehydrate them, but they must dry completely before being returned to storage to prevent mold.
Waking Up Geraniums in the Spring
The transition back to active growth should begin approximately six to eight weeks before the last expected frost date in your region. For dormant, bare-root plants, the process starts with removing them from storage and pruning back any dead or shriveled tissue to firm, green growth. The roots should then be soaked in warm water for one to two hours to rehydrate the plant’s vascular system.
The rehydrated bare-root geraniums are then potted into fresh potting mix, given a thorough initial watering, and placed in a bright, sunny location. Plants that were overwintered in pots should be pruned back by one-half to two-thirds to encourage new, bushy growth rather than long, leggy stems. Once new growth is visible, watering frequency can be gradually increased, and a diluted liquid fertilizer can be introduced to support the plant’s revival. “Hardening off,” a gradual process that slowly acclimatizes them to outdoor conditions over one to two weeks, is the final step before moving the geraniums back outside after the danger of frost has passed.