The plant commonly called Citronella is usually the scented geranium (Pelargonium citrosum or a hybrid), not the true Citronella Grass (Cymbopogon nardus). These tender perennials are native to tropical regions and are only reliably hardy in USDA zones 9 through 11, meaning they cannot withstand freezing temperatures. Successfully overwintering requires moving the plant indoors or providing significant protection to keep the root structure safe from frost. Success depends on proper preparation and selecting the right method based on climate and available indoor space.
Preparing Citronella for Dormancy
Preparation for winter begins before the first expected frost, typically when nighttime temperatures consistently fall below 50°F. Prune the plant back significantly, removing dead or yellowing foliage and cutting the stems by about one-half to two-thirds. This reduction minimizes the plant’s moisture needs and makes it more manageable for indoor placement.
Before bringing container plants indoors, thoroughly inspect them for pests to prevent home infestations. Check the undersides of leaves and the soil surface for common issues like whiteflies, spider mites, or aphids. If pests are detected, treat the plant with an insecticidal soap before moving it.
To prepare for winter rest, slow the plant’s metabolism by manipulating its care regimen. Greatly reduce watering frequency, allowing the soil to dry out more completely between waterings. Stop all fertilization entirely, as the plant will not be actively growing and excess nutrients can cause weak growth during the winter.
Indoor Overwintering Methods
The most common overwintering method is treating the plant as a houseplant, maintaining slow, active growth. Place the potted plant in a location that receives bright, direct sunlight, such as a south-facing window, to support the remaining foliage. Ideal temperatures range between 55°F and 65°F, encouraging the plant to slow growth without entering deep dormancy.
During this phase, water sparingly, only when the top inch of soil is completely dry. Overwatering is the most common cause of failure, leading to root rot in cool, low-light conditions. If the plant becomes “leggy” with long, weak stems, pinch back the growing tips to encourage a bushier, more compact shape.
Forced dormancy is an option if bright indoor space is limited, requiring a cool, dark, and frost-free location like a basement or garage. Temperatures should remain consistently cool, ideally between 35°F and 45°F, just above freezing. The plant can be stored in its pot or, to save space, dug up, shaken free of soil, and stored bare-root in an open box.
Stored plants should receive minimal to no water; the goal is to prevent the roots from completely desiccating, not to encourage growth. If the stems appear wrinkled or overly dry, a light, infrequent misting or a brief soaking of the roots can provide moisture. This method causes the leaves to drop, but the plant retains viable stems and roots for the spring.
Outdoor Protection in Mild Climates
Leaving the Citronella plant outdoors is only feasible in warm regions (USDA hardiness zones 10 and 11) where temperatures rarely dip below freezing. In these environments, the plant continues to grow through the winter, though at a much slower rate. The primary concern is protecting the plant from unexpected, short-duration cold snaps.
For potted plants, moving them against a warm, sheltered structure, such as a house wall or covered patio, provides temperature protection. The structure’s thermal mass radiates heat, moderating the microclimate around the container. For in-ground plants, applying a thick layer of organic mulch (straw or wood chips) around the base helps insulate the root zone.
When a freeze is predicted, immediately cover the plants. Use a specialized row cover or frost cloth draped over the foliage, ensuring the material extends to the ground to trap residual heat. This temporary covering protects the plant from damage during brief dips below freezing.
Spring Transition and Reintroduction
Once the danger of the last expected frost has passed, the Citronella plant can be prepared for its return outdoors. Plants kept dormant in a cool, dark location should be gradually awakened by increasing light and moisture. The first step is to repot or refresh the soil, providing new potting mix to encourage robust root growth.
Increase the watering volume and frequency, ensuring the soil is consistently moist but never soggy. Introduce a diluted liquid fertilizer to stimulate new growth and replenish nutrients. Prune away any remaining dead or woody stems to shape the plant and promote fresh, vigorous shoots.
The plant must then undergo “hardening off” to acclimate it to the harsher outdoor environment. Start by placing the container in a sheltered location with dappled shade for a few hours each day. Over seven to ten days, gradually increase the plant’s exposure to direct sunlight, wind, and cooler night temperatures. This slow adjustment prevents sun scald and transplant shock, ensuring a smooth transition to its final summer location.