Citronella Geranium
Citronella geranium (mosquito plant) grows as a tender annual in US gardens. Learn care, overwintering, and what research says about mosquito repelling.
Key takeaways
- Pelargonium citrosum is a South African tender perennial grown as an annual in Zones 3–8 and as a perennial only in Zones 9–11
- Intact plants do not repel mosquitoes — university studies found no measurable effect; the scent requires brushing or crushing leaves
- Full sun (6+ hours daily) and fast-draining potting mix are essential — wet roots cause crown rot within days
- Fertilize with a balanced 10-10-10 fertilizer every 3–4 weeks through summer to sustain vigorous, fragrant growth
- Take 4-inch stem cuttings in late August to overwinter plants indoors and avoid buying new $8–$15 pots each spring
What is citronella geranium?
Citronella geranium is Pelargonium citrosum, a South African tender perennial sold across the US as a patio mosquito repellent. Research does not support the repellent claim for intact plants. It is, however, a fragrant, easy-to-grow container plant that earns its spot on any sunny porch.
US retailers market it under several names: Citrosa Geranium, Mosquito Plant, Lemon Geranium. The confusion with true geraniums (Geranium spp.) runs deep. True geraniums are hardy perennials that survive Zone 4 winters. Pelargonium citrosum is frost-tender and dies at 32°F without protection. The only thing the two groups share is the word “geranium” in common usage.
The plant’s leaves smell strongly of citronella when touched. That scent comes from citronellol, geraniol, and citronellal — the same volatile compounds found in commercial citronella candles and sprays, though in a different ratio. The marketing pitch follows from there. The science does not.
Does citronella geranium repel mosquitoes?
Published university research shows intact citronella geranium plants provide no statistically significant mosquito protection at normal patio distances. The repellent compounds are only released when leaves are physically disturbed.
A frequently cited study tested mosquito attraction near undisturbed Pelargonium citrosum plants in field conditions. Researchers found no reduction in mosquito landings compared with control areas. The plant’s volatile emissions in ambient air are too dilute to affect mosquito behavior. The same finding has been replicated in multiple university extension evaluations across the US.
What rubbing a leaf on your skin can do: crushed leaf oils applied directly to skin provide brief, localized deterrence — roughly 15–30 minutes of mild protection. This is far weaker than DEET, picaridin, or IR3535-based repellents, which the CDC recommends for US mosquito-borne disease prevention. It is comparable to rubbing citronella candle wax on skin, which is not a recommended practice either.
| Mosquito protection method | Proven repellent effect | Duration |
|---|---|---|
| Citronella geranium — intact plant | None | — |
| Citronella geranium — rubbed leaf on skin | Mild | 15–30 minutes |
| Citronella candle (outdoors, still air) | Moderate, short-range | While burning |
| DEET 25–30% | High | 6–8 hours |
| Picaridin 20% | High | 8–12 hours |
| Citronella grass (Cymbopogon) — rubbed leaf | Mild | 15–30 minutes |
Source: CDC guidelines for mosquito repellent selection (cdc.gov/niosh/topics/emres/repellent.html).
Despite the overstated marketing, citronella geranium still attracts gardeners for good reasons. The fragrance is pleasant. The plant is fast-growing and showy. It handles US summer heat well in containers. And knowing it does not repel mosquitoes frees you from disappointment when you still get bitten.
Citronella geranium vs. true citronella grass
Citronella grass (Cymbopogon nardus or C. winterianus) is the actual source of commercial citronella oil. It is a large clumping grass that grows to 5–6 feet tall. It is rated for USDA Zones 10–12 and is grown commercially for essential oil extraction in Sri Lanka, Java, and parts of Central America.
In the US, citronella grass is rarely sold at retail. It performs poorly as a patio plant — it does not make a compact, attractive container specimen, and it has no additional ornamental value. Citronella geranium is sold instead partly because it fills that retail niche and partly because the name sounds right.
If you want citronella scent outdoors, citronella geranium is the practical US option for containers and patios. If you want actual mosquito protection, use an EPA-registered repellent product.
Sun, site, and container requirements
Full sun — 6 or more hours of direct sunlight daily — is non-negotiable for healthy citronella geranium growth. Insufficient light results in leggy stems, sparse leaves, and weak fragrance.
South-facing or west-facing placement works best for most US locations. In the hottest parts of Zones 9–11 (Phoenix, Las Vegas, south Texas), afternoon shade from about 2–5 PM prevents leaf scorch during extreme heat above 100°F.
Container size: Use a pot at least 12 inches in diameter. A 14–16-inch container allows a full season of growth without needing to upsize. Larger containers hold more soil volume and dry out more slowly, reducing the frequency of watering in summer heat.
Container material: Terracotta and unglazed ceramic allow water to wick through the walls, which reduces overwatering risk. Plastic and glazed ceramic hold moisture longer — if you use them, water even less frequently than with terracotta.
Drainage: Every container must have drainage holes. A citronella geranium sitting in water for 24 hours begins to develop root rot. There is no recovery from advanced root rot.
For potting mix advice that also applies to this plant, see best soil for indoor plants.
Watering
Water citronella geranium when the top 1 inch of potting mix feels dry. In a 14-inch terracotta pot in summer sun, this is roughly every 3–5 days. Check the soil, not the calendar.
Pelargoniums evolved in seasonally dry South African conditions. They tolerate brief dryness far better than sustained wet soil. A plant that wilts slightly from underwatering recovers quickly after watering. A plant with root rot from overwatering rarely recovers.
Signs of overwatering: yellowing lower leaves, soft or mushy stem base, foul-smelling potting mix, wilting that does not improve after watering.
Signs of underwatering: dry, slightly wilted leaves that perk up within hours of watering, potting mix completely dry several inches down.
In the hottest US climates (Zones 9–11 in summer), plants in smaller containers may need daily watering when temperatures exceed 95°F. Always water thoroughly — water should drain from the bottom holes, not just wet the top inch.
Fertilizing
Feed with a balanced granular or liquid fertilizer every 3–4 weeks through the growing season. A 10-10-10 or similar balanced ratio supports steady leaf and stem growth. Phosphorus-heavy formulas (5-15-5) encourage more blooms.
Citronella geraniums are moderate feeders. They do not need heavy fertilization, but plants growing in containers leach nutrients faster than garden beds — regular feeding maintains healthy color and vigorous growth.
Stop fertilizing in September for plants you plan to overwinter indoors. Reducing fertilizer slows growth and prepares the plant for lower light and cooler temperatures inside.
Pruning for bushy growth
Pinch growing tips every 2–3 weeks through summer. Each pinched tip produces two branches. A regularly pinched plant stays compact and grows more fragrant leaves than an unpruned one.
To pinch: use your thumb and forefinger to snap off the top 1–2 inches of each stem just above a leaf node. Pruning shears work equally well. The removed tips can be used as cuttings for propagation.
Deadheading spent flowers is optional. It keeps the plant looking neat and may prolong the blooming period, but citronella geranium is grown primarily for foliage, not flowers.
Cut back leggy or overgrown plants by up to one-third in midsummer to encourage a fresh flush of compact new growth.
Overwintering in the US
In USDA Zone 8 and colder, citronella geranium does not survive outdoors through winter. Bring containers indoors before the first frost or take cuttings to maintain plants without the full-size space requirement.
Moving the whole plant indoors: Place in the brightest available window — south-facing is ideal. Supplemental grow lights extend the light hours in winter. Cut the plant back by 50% before bringing indoors to reduce water and light demand. Water sparingly — once every 10–14 days in winter.
Taking cuttings in late summer (recommended for most gardeners):
- In late August, select healthy stems without flower buds.
- Cut 4-inch sections just below a leaf node.
- Remove the lower two sets of leaves to expose stem for rooting.
- Dip cut ends in rooting hormone powder (optional).
- Insert into small pots of moist perlite or potting mix.
- Cover loosely with a clear plastic bag to maintain humidity.
- Place in a warm location — 65–70°F — with indirect light.
- Roots develop in 3–5 weeks. Remove the bag once roots appear.
- Grow under a grow light through winter at 12–14 hours per day.
- Move outdoors after the last frost date the following spring.
Buying new plants each spring: Widely available at Home Depot, Lowe’s, and local nurseries in spring for $8–$15 per pot. For gardeners without indoor grow space, replacing annually is a practical choice.
Propagation from cuttings
Cuttings taken from pinched stems work just as well as dedicated cutting sessions. Any time you pinch back the plant during summer, you can root the removed tips. Small pots of perlite or a 50/50 perlite and potting mix blend root citronella geranium cuttings reliably.
Cuttings taken earlier in the season (June–July) produce larger plants for overwintering indoors. August cuttings still work but produce smaller plants by spring. Either size transplants outdoors successfully after the last frost.
Common pests and problems
Aphids and whiteflies are the most frequent pest problems for citronella geranium in US gardens. Fungal issues appear when plants are overwatered or air circulation is poor.
Aphids: small, soft-bodied insects clustered on new growth. Knock off with a strong water spray. Insecticidal soap spray works for heavier infestations. For background on aphid management, see the general guide at geranium care.
Botrytis blight: gray fuzzy mold on stems and leaves in wet, cool weather. Remove affected parts immediately. Improve air circulation. Avoid overhead watering.
Root rot: mushy, dark roots from overwatering. Usually fatal. Prevention — proper containers with drainage holes and a check-soil-before-watering routine — is the only reliable strategy.
Rust (orange pustules on leaf undersides): common in humid eastern US climates. Remove affected leaves and avoid overhead watering. Improve air circulation. Copper-based fungicide sprays work preventively.
For information on the broader geranium family and which types suit US gardens best, see perennial geranium and attract pollinators to your garden.
Sarah Mitchell is a Master Gardener and garden writer based in the Pacific Northwest. She has been growing food and flowers for over 15 years across USDA zones 7 and 8.