The plant commonly sold as “citronella plant” is often Pelargonium citrosum, a scented geranium known for its mosquito-repelling fragrance. While it thrives outdoors, this perennial is not cold-hardy and cannot survive freezing temperatures. For gardeners in temperate regions, successful overwintering requires strategic pruning before cold weather arrives. This preparation ensures the plant can be safely stored indoors until spring, maintaining its health and vigor.
Preparing the Plant: Timing the Cut
Determining the correct moment to prune is more about monitoring the environment than following a calendar date. The goal is to perform the cut after the plant naturally begins to slow its growth, but well before the first severe frost. This window typically occurs when nighttime temperatures consistently drop below 50°F (10°C).
The plant responds to shorter daylight hours and cooler air by entering a state of semi-dormancy, which reduces its energy expenditure. Waiting until this natural slowdown occurs minimizes stress on the plant following the pruning action. Observing visual cues, such as a reduction in new leaf production and slightly faded foliage color, confirms the plant is ready for its transition indoors.
Pruning too early can stimulate tender new growth that is vulnerable to cold shock. Waiting too long risks damage from an unexpected early freeze.
Essential Pruning Techniques
Before making any cuts, ensure all tools are sharp and sterilized. Using clean pruning shears prevents the transfer of potential pathogens into the fresh wounds. Wiping down tools with rubbing alcohol or a bleach solution before and after use maintains hygiene.
The primary objective of this winter prune is to reduce the plant’s overall size for easier storage and to remove any weak or damaged material. Aim to reduce the plant by approximately one-half to two-thirds of its current height and spread.
When making cuts, always locate a node, the swollen area on the stem where a leaf or branch emerges. Cut just above a healthy node, typically about a quarter-inch above it. This encourages new, outward-facing growth when the plant breaks dormancy in the spring, promoting a fuller, bushier shape.
Selectively remove any dead, yellowing, or diseased stems completely, cutting them back to the main stem or soil line. Ensure that no ragged edges are left behind to maintain the structural integrity of the remaining healthy branches. Clean, precise cuts heal faster and minimize the surface area through which pathogens might enter.
Winter Storage and Dormancy Care
Do not move the citronella plant indoors immediately after pruning, as the fresh cuts need time to dry out and form a protective layer, known as callusing. Allowing the plant to rest outdoors in a sheltered area for two to five days encourages this protective barrier to form, significantly reducing the risk of fungal infection once moved to a less ventilated indoor environment. During this callusing period, significantly reduce watering.
Once the cuts have sealed, choose between two main overwintering methods: maintaining active indoor growth or inducing full dormancy. For active growth, place the plant in a location receiving at least six hours of bright, indirect sunlight daily, such as a south-facing window. Maintain temperatures in a cool range, ideally between 55°F and 65°F (13°C to 18°C), to prevent excessive stretching and weak growth.
The active storage method requires minimal watering; allow the top inch or two of soil to become dry between applications. Overwatering is a common cause of failure, leading to root rot when the plant’s metabolic rate is low. Stop fertilization completely during this period, as the plant is not actively producing energy for significant new growth.
Alternatively, the plant can be forced into a deep dormancy, which is useful when bright indoor light is unavailable. Place the drastically pruned plant in a cool, dark location, such as a basement or garage, where temperatures remain just above freezing, around 40°F to 50°F (4°C to 10°C). In this state, the plant requires almost no water, perhaps a small splash once a month to prevent the roots from completely desiccating. This method requires less attention and space.