The question of whether the citronella plant is an annual or a perennial is a common point of confusion for gardeners. This plant, often purchased for its fragrant foliage, does not fit neatly into one category, as its life cycle depends entirely on the climate in which it is grown. The answer is conditional, rooted in the plant’s tender nature and its inability to withstand freezing temperatures. Understanding the plant’s identity is the first step toward determining how to care for it year after year.
The Identity Crisis: What is the “Citronella Plant”?
The plant most frequently sold as the “Citronella Plant” or “Mosquito Plant” is a type of scented geranium, scientifically known as Pelargonium citrosum or a similar hybrid. This subshrub is characterized by lacy, serrated leaves that release a strong, lemon-like aroma when crushed. Despite its common name, this plant is botanically distinct from the species that produce commercial citronella oil.
The true source of the essential oil used in repellents is Citronella Grass, Cymbopogon nardus, which belongs to the grass family. While both plants share a similar citrus scent and thrive in warm temperatures, the scented geranium (Pelargonium) is the one most commonly grown in containers for seasonal patio use.
Determining the Life Cycle Status
The scented geranium is classified as a tender perennial, meaning it lives for more than two years but is sensitive to cold. In regions with mild, frost-free winters (USDA Hardiness Zones 9 through 11), the plant can remain outdoors year-round and maintain its perennial status. In these warm climates, the plant develops a woody base and continues to grow season after season.
The plant is intolerant of freezing temperatures; exposure to frost will cause it to die back completely. In the majority of regions falling into Zone 8 and below, the plant must be treated as an annual. Gardeners often allow the plant to perish at the end of the season, replacing it with a new specimen the following spring. The life cycle status is determined by the local climate, turning a natural perennial into a temporary annual for many growers.
Essential Care for Summer Growth
To promote robust summer growth, the scented geranium requires sufficient light exposure. The plant thrives best in full sun, receiving at least four to six hours of direct sunlight each day. In climates with intense afternoon heat, providing partial shade can prevent the foliage from becoming stressed or scorched.
The soil must be well-draining, as the plant will quickly languish in waterlogged conditions. Use a loamy, sandy mix that allows water to pass through freely, especially when grown in a container. Watering should be deep and thorough, allowing the top inch or two of soil to dry out completely before re-applying water. The plant is a light feeder; while potted specimens benefit from a diluted liquid fertilizer every three to four weeks during the active growing season, excessive feeding can weaken the concentration of fragrant oils.
Steps for Successful Overwintering
Since the citronella geranium is naturally a perennial, it can be saved from winter frost and grown again the next year. The process begins in the fall, before the first hard frost, or when night temperatures consistently drop below 50°F. The plant must first be inspected and cleared of any pests or diseases that could spread inside the home.
Overwintering as a Houseplant
One practical method is to bring the entire potted plant indoors to be grown as a houseplant. Before moving it, cut the stems back by one-third to one-half to reduce growth and help the plant focus its energy. Once inside, the plant prefers a bright, sunny location, such as a south-facing window, and cooler room temperatures, ideally between 60°F and 65°F.
Dormant Storage
During the winter months, the plant’s growth slows significantly, requiring a reduction in water. Water only when the top couple of inches of soil are dry, and cease all fertilizer application until spring. Alternatively, the plant can be forced into a dormant state by digging it up, shaking off most of the soil, and storing it bare-root in a cool, dark, and dry location, such as an unheated basement or cellar. This storage area should maintain a temperature between 45°F and 60°F, and the plant should not be watered until it is repotted in the spring.