Citronella plants, celebrated for their distinct citrus aroma and perceived ability to deter mosquitoes, are a popular addition to many gardens and patios. These herbaceous perennials, often identified as Pelargonium citrosum or Pelargonium graveolens, are tender and cannot withstand freezing temperatures. In regions experiencing cold winters, winterizing citronella plants becomes necessary to ensure their survival. Without proper protection, these plants, which are perennial only in USDA Zones 9-11, will perish in colder climates.
When to Prepare Citronella for Winter
Citronella plants are sensitive to cold, making precise timing for winterization important. Bring container-grown citronella indoors or provide protection to outdoor plants before the first frost. Nighttime temperatures consistently dropping below 45°F (7°C) signal the need for immediate action, as these plants are not frost-hardy. Waiting too long can hinder the plant’s adjustment to indoor conditions and lead to damage.
Winterizing Citronella Plants Indoors
Bringing citronella plants indoors for the colder months is a common and effective strategy to protect them from harsh winter conditions.
Pre-Winter Preparation
Before relocating your citronella plant indoors, prepare it. Prune the plant back by up to one-third, or cut stems to 6 to 8 inches tall, to manage its size and encourage bushier growth. This pruning should occur just above a leaf node. Inspect the plant for pests like aphids, whiteflies, or mealybugs, treating any infestations before moving it inside. If root-bound, repot into a pot at least 12 inches deep with good drainage.
Indoor Environment
Once indoors, provide suitable conditions for your citronella to thrive. Place the plant in a location that receives bright, indirect sunlight, ideally a south or west-facing window, ensuring at least six hours of light daily. Supplemental grow lights may be necessary if natural light is insufficient, keeping the plant within a few inches of the light source for 12-18 hours daily.
Reduce watering frequency, allowing the soil to dry out slightly between waterings, typically when the top inch or two of soil feels dry. Overwatering can lead to root rot. Maintain indoor temperatures between 50°F and 80°F (10°C to 27°C), and aim for humidity levels of 40% or higher, achieved through misting or pebble trays.
Winterizing Citronella Plants Outdoors
In milder climates, citronella plants can sometimes be winterized outdoors, though this approach is generally limited to specific hardiness zones.
Pruning for Outdoor Winterization
For citronella plants remaining outdoors, pruning strategies vary by climate severity. In very mild climates, a light topping back to maintain shape may suffice. In areas with marginal hardiness, cut the plant back significantly after the threat of frost has passed, or after a light frost. Removing dead or damaged leaves and stems after frost allows the plant to conserve energy.
Ground Protection
To protect roots from freezing, apply a thick layer of mulch, such as straw, shredded leaves, or wood chips, around the base of the plant. This insulation helps regulate soil temperature and retain moisture. During severe cold snaps, covering the entire plant with burlap or frost cloth offers additional protection from freezing winds and temperatures. Outdoor winterization is most effective in USDA Hardiness Zones 9-11, or for brief, mild winter periods, as sustained freezing temperatures will likely prove fatal.
Reintroducing Citronella in Spring
Successfully transitioning citronella plants back outdoors in spring requires a gradual approach to prevent shock. Once the danger of frost has passed and nighttime temperatures consistently remain above 50°F (10°C), begin the reintroduction process.
Gradually acclimate the plants to outdoor conditions over one to two weeks, a process known as “hardening off.” Begin by placing them in a shaded, sheltered location for a few hours daily, progressively increasing exposure to direct sunlight and wind. This allows the plant to adjust to stronger outdoor light and fluctuating temperatures. Increase watering frequency as the plant resumes active growth, ensuring the soil remains consistently moist but not waterlogged. Consider applying a balanced, slow-release fertilizer to encourage vigorous new growth and replenish nutrients.