The vibrant plants commonly known as geraniums are actually Pelargonium species, which are tender perennials native to warmer climates. These plants cannot withstand the freezing temperatures of a cold winter and will perish if left outside after the first hard frost. Saving your favorite varieties requires intentionally moving them into a protected environment to induce a state of winter dormancy or to maintain active growth indoors. Successfully overwintering these plants ensures you can enjoy their colorful blooms and foliage again in the spring without the expense of buying new stock.
Preparing Plants for Winter Storage
The process of preparing your geraniums must begin well before the first overnight temperature drops below freezing. Geraniums are susceptible to even a light frost, so monitor the forecast and act proactively. Before moving any plant indoors, thoroughly inspect the foliage and stems for signs of pests, such as whiteflies or spider mites, or fungal diseases. Selecting only the healthiest specimens prevents an infestation from spreading to other houseplants.
The plant should then be pruned to reduce its overall size, which prepares it for storage and minimizes moisture loss. Cutting back the stems by about one-third to one-half of their current length is a standard recommendation. This initial pruning helps the plant conserve energy and encourages new, bushier growth when it wakes up from its winter rest. Cleaning the plant by removing all dead leaves, spent flowers, and debris from the soil surface is the final step before moving it to its intended winter location.
The Bare-Root Dormancy Method
The bare-root method is a space-saving technique that encourages deep dormancy by simulating the plant’s natural resting period. Carefully dig the entire plant out of the garden or container before the soil freezes, preserving the root system. Gently shake the plant to remove the majority of the surrounding dirt until the roots are mostly exposed. Removing excess soil is important because it can retain too much moisture and lead to fungal growth during storage.
The prepared plants can be stored by either hanging them upside down or placing one or two plants inside a large brown paper bag or perforated cardboard box. This storage container should be placed in a cool, dark, and dry location, such as an unheated basement or root cellar. The temperature in the storage area should ideally remain stable between 45 and 55 degrees Fahrenheit to maintain dormancy without freezing the root crown. The lack of light and cool temperatures will cause the remaining leaves to dry up and fall off, signaling that the plant has entered its dormant state.
While dormant, the plant still requires minimal moisture to prevent complete desiccation of the root system. Check the plants monthly; if the stems appear shriveled or the roots feel excessively dry, briefly rehydrate them. Soak the roots in lukewarm water for about an hour, allowing them to air-dry fully before returning them to storage. Avoid storing them in plastic bags or sealed containers, as this traps moisture and promotes mold and rot.
Overwintering Geraniums as Houseplants
The alternative to dormancy is maintaining the geraniums as actively growing houseplants, which works well if the plants are already in containers. If they were in the ground, dig them up and repot them into containers using fresh potting mix that has excellent drainage. This method requires adjusting environmental conditions to keep the plant healthy over the winter. Adequate light is necessary for active growth, so place potted geraniums in a south-facing window receiving six to eight hours of direct sunlight.
If natural light is limited, supplemental light from a simple fluorescent or LED grow light for 12 to 16 hours a day can prevent the stems from becoming weak and elongated. Geraniums prefer slightly cooler indoor temperatures, ideally around 60 to 70 degrees Fahrenheit during the day, with a small temperature drop at night. Water management is significantly reduced during the winter; only water the plants when the top inch of soil feels dry to the touch. Cease all fertilizer application during this period, as the plant is in a reduced-growth state and does not require additional nutrients.
Bringing Geraniums Back to Life in Spring
The transition from winter storage to spring growth should begin six to eight weeks before the last expected frost date. For bare-root plants, remove them from storage and prune stems back to firm, green tissue, removing any shriveled or dead material. Soaking the bare roots in water for an hour or two will rehydrate the plant tissues for replanting. Immediately pot the dormant plants in fresh, well-draining potting soil and water thoroughly.
Place the newly potted geraniums in a bright window or under grow lights to initiate new growth. Once new leaves emerge, gradually increase watering frequency and introduce a diluted, balanced liquid fertilizer. Geraniums overwintered as houseplants require a final, aggressive pruning to remove leggy, sparse winter growth.
The final step for all overwintered plants is hardening off before moving them permanently outdoors after the danger of frost has passed. Hardening off involves incrementally exposing the plants to outdoor conditions—starting with a few hours of shade daily—over one to two weeks to prevent shock.