Walk into almost any garden center in late spring and you’ll find a leafy, lacy-leaved plant labeled “citronella plant” or “mosquito plant,” promising to keep your patio bite-free all summer. Crush a leaf and it smells exactly like the citronella candles you light at a backyard cookout, so the marketing writes itself. The trouble is that the citronella plant sold in pots and the citronella that actually goes into those candles and sprays are two completely different plants, and only one of them does anything to mosquitoes.
The plant you buy is a scented geranium, Pelargonium ‘Citrosum,’ and despite its nickname, the evidence that it repels mosquitoes is thin to nonexistent. The real citronella oil comes from a tropical grass, Cymbopogon nardus, that you’ve probably never seen on a nursery bench. Both are worth growing, but for honest reasons. Here’s how to tell them apart, how to grow and care for each one, how to carry them through winter, and what the research really says about that mosquito-repelling promise.
The citronella plant you buy is a scented geranium, not citronella
The plant marketed as the citronella plant or mosquito plant is Pelargonium ‘Citrosum,’ also sold under names like citrosa geranium, Pelargonium citrosum ‘Van Leenii,’ citranium, or branded names like “Mozzie Buster.” It belongs to the genus Pelargonium, the group most people simply call geraniums, even though true geraniums are a separate genus. Botanically the species “P. citrosum” doesn’t really exist as a valid name; the plant is almost certainly a cultivar of the rose-scented geranium Pelargonium graveolens, which is why you’ll often see it written as Pelargonium ‘Citrosum’ in single quotes.
It’s a tender, bushy perennial with crinkled, deeply cut, lacy green foliage that grows roughly 2 to 3 feet tall and can spread up to 4 feet wide in a good season. In summer it produces small clusters of pink to lavender flowers, but nobody grows it for the blooms. The draw is the scent: brush past the plant or crush a leaf and it releases a bright, lasting lemon-citrus fragrance that’s strikingly similar to true citronella oil. That single resemblance, smell, is the entire basis for its reputation.
Like other scented geraniums, the leaves are edible and carry a citrusy flavor. Gardeners use them the way they’d use lemon-scented herbs: tucked into the bottom of a cake pan before the batter goes in, steeped into jellies and teas, or dropped into fruit salads and summer desserts. Snip a few stems for a vase, too, the lacy leaves hold other flowers in place and perfume the table.
Where the mosquito-plant name came from
The mosquito reputation isn’t an accident, it was a marketing campaign. In the 1980s a Dutch plant breeder named Dirk van Leenen introduced this geranium to the houseplant world, pushing it hard in Florida where mosquitoes make outdoor life miserable. Van Leenen claimed his plant was a laboratory hybrid created by splicing African Pelargonium with lemongrass through tissue culture, supposedly back in the mid-1970s. That story is botanical fiction, the gene-splicing technology he described didn’t exist then, and you can’t simply fuse a grass and a geranium that way. But the “citrosum” and “Van Leenii” names stuck, and so did the promise. A 1992 magazine article cheerfully called it a “skeeter skeedaddler,” and the nickname mosquito plant has followed it around ever since.
Do citronella plants actually repel mosquitoes? An honest answer
Short version: no. Growing a Pelargonium ‘Citrosum’ on your patio will not keep mosquitoes off you, and the research is remarkably consistent on this point.
The compound that gives citronella its insect-repelling power is called citronellal. The oil in the citronella geranium contains only about 0.09% citronellal. By comparison, the oil from true citronella grass runs around 14% citronellal, roughly 150 times more concentrated. That gap alone explains why the geranium does almost nothing.
It gets worse for the marketing claim. In a 1994 field study, researchers Cilek and Schreiber tested the “mosquito plant” against Aedes albopictus and Culex quinquefasciatus in Florida and found it failed to repel either species, human subjects sitting near the plants got bitten just as much as controls. In trials, mosquitoes have been observed landing on the plant itself. The smell that’s so appealing to us simply doesn’t bother them.
What about crushing the leaves and rubbing them on your skin? Even that is unreliable. The living plant releases far too little oil to matter, and the sap can irritate sensitive skin or trigger an allergic rash. Bruising a leaf gives off a pleasant scent and maybe the faintest, briefest deterrent at most, nothing close to a real repellent. The honest takeaway: grow the citronella geranium because it’s an attractive, fragrant, easy plant, not because it will protect you from bites.
True citronella comes from a tropical grass
The citronella oil in candles, sprays, and torches is steam-distilled from grasses in the genus Cymbopogon, most often Cymbopogon nardus (Ceylon citronella) and the closely related Cymbopogon winterianus (Java citronella). These are tall, clumping, tropical grasses, the same family as lemongrass, reaching up to 5 or 6 feet, with arching blades and a strong lemony aroma. This is the plant that earns the citronella name.
Unlike the geranium, the oil from Cymbopogon grasses has genuine, scientifically documented activity, it works as an insect repellent, an insecticide, and a mosquito larvicide. The evidence isn’t airtight on every front: the oil is registered as a repellent in the United States, while the EU pulled its registration as an insecticide for lack of validated efficacy, so “how well and how long” remains debatable. But the active chemistry is real, which is exactly what the geranium lacks.
One important caveat: even with the real grass, simply growing it in the ground won’t fog your yard with repellent. The oil has to be extracted and applied to do anything, and rubbing a raw blade of grass on your arm does little beyond risking a paper-cut-style scrape. The plant is the source of the oil, not a substitute for it.
How to grow and care for the citronella scented geranium
For all the mosquito confusion, Pelargonium ‘Citrosum’ is a genuinely rewarding, low-fuss plant. It’s grown as an annual across most of the country and as a tender perennial only in USDA zones 9 through 11.
When and where to plant. Set plants out in spring only after all danger of frost has passed and the soil has warmed, the same timing you’d use for tomatoes or peppers. Harden off nursery plants for about two weeks first if they’ve been under cover. Choose a spot with good drainage and full sun to part shade; six to eight hours of sun is ideal, though the plant does fine on four to six, and a little afternoon shade is welcome in hot-summer regions. Space plants 18 to 24 inches apart.
Soil. It isn’t fussy, but it grows best in moderately rich, well-drained soil. Work a few inches of aged compost into the bed before planting. In containers, use a quality potting mix and make sure the pot has drainage holes, soggy roots are this plant’s biggest enemy.
Watering. Aim for balance. The geranium likes moisture but despises “wet feet,” and overwatering leads straight to root rot. Let the top inch of soil dry out before watering again, and check with a finger rather than watering on a fixed schedule. Plants in the ground are fairly drought-tolerant once established; those in pots dry out faster and need more frequent attention in summer heat.
Fertilizing. In good garden soil, plants rarely need feeding, a 2-inch mulch of compost is plenty. Container plants are different, since potting mix holds few nutrients; feed them about once a month during the growing season with a water-soluble fertilizer. Skip high-phosphorus “bloom booster” formulas, and don’t overfeed, too much nitrogen pushes lush leaves at the expense of flowers.
Pruning. Little is required. Pinch the growing tips to encourage a bushier, fuller plant, and remove lower leaves as they yellow with age. Deadhead spent flowers to keep more coming, and snip stems freely for arrangements, the plant responds well to cutting.
Propagation. This geranium roots almost embarrassingly easily from cuttings, which is faster and more reliable than seed. Cut a healthy stem tip 3 to 5 inches long with two to four nodes, strip the lower leaves, and either set it in a glass of water or push it into moist potting mix or perlite. Rooting hormone speeds things up but isn’t necessary. Cover a soil cutting loosely to hold humidity, keep it in bright indirect light, and expect roots in two to three weeks (a little longer in winter’s lower light). A gentle tug that meets resistance tells you it has rooted. Seed is possible but slow; start it indoors at room temperature, where it germinates in one to two weeks.
Repotting. Most plants grow as a single main stem and don’t offset, so division usually isn’t an option. Instead, step a crowded plant up one pot size in spring, or prune it hard to keep it in bounds. Refresh the soil every other year.
How to grow citronella grass, the real thing
If you want the plant that actually produces citronella oil, seek out Cymbopogon nardus or C. winterianus, sometimes labeled citronella grass or mosquito grass. It’s grown the same way as its cousin lemongrass.
Climate and siting. Citronella grass is a true tropical, hardy outdoors only in USDA zones 9 to 11 (some growers push it to 10 in colder microclimates). Anything below freezing damages or kills it, so most gardeners north of those zones grow it in a large pot or treat it as an annual. Give it full sun to bright, lightly dappled light, six to eight hours a day, and plenty of room; a single clump can reach 5 to 6 feet tall and wide.
Soil and water. Plant in fertile, well-draining soil enriched with organic matter; in pots, lighten the mix with perlite or coir for drainage. Unlike the drought-tolerant geranium, the grass is a heavier drinker and prefers consistently moist soil, especially during active summer growth and dry spells. Even so, it won’t tolerate standing water, soggy roots invite rot and fungus gnats.
Feeding and propagation. As a fast, leafy grower it appreciates regular feeding through the growing season with a balanced fertilizer. It rarely sets viable seed, so it’s propagated almost entirely by division: in spring or early summer, lift a mature clump and split it into sections of three to five tillers, each with healthy roots, then replant.
How to overwinter citronella plants and grass
Both plants are tender, and in most of the country the season ends at the first hard frost unless you intervene. You have a few options.
Let it go. The simplest approach is to treat either plant as an annual and compost it after frost. There’s no shame in starting fresh each spring.
Bring the geranium indoors as a houseplant. Before frost, dig up the geranium, shake off most of the soil, cut it back to about 6 inches, and pot it in fresh potting mix. Place it in your brightest window, a south-facing exposure or under grow lights, since indoor plants tend to stretch and go leggy in low winter light. It actually prefers cooler indoor temperatures, around 60 to 65°F, than most homes provide, and humidity above 40%. Water only when the top inch dries, hold off on fertilizer until growth resumes, and pinch back any lanky stems. Harden it off before moving it back outside after spring frosts pass.
Store the geranium bare-root and dormant. A space-saving trick: dig the plant, knock off the soil, cut it back to about 10 inches, and set it in a cardboard box in a dark, dry, cool spot (45 to 50°F) that won’t freeze. The leaves drop but the green stems survive. Check monthly, misting lightly if the stems shrivel, but never let them get damp enough to mold. A month or two before your last frost, pot it up in a warm, bright spot to wake it, then plant it out after frost.
Take cuttings instead of saving the big plant. Often the easiest route for the geranium is to root a few late-summer cuttings (see the propagation steps above) and overwinter the small starts on a windowsill. They take up little room and give you fresh, vigorous plants, and several at once, for spring.
Overwinter the grass in a pot. Citronella grass is best lifted into a container and moved to a frost-free spot for winter, since it won’t survive freezing ground in most zones. Keep it in bright light, water sparingly while growth slows, and prioritize drainage, most winter losses come from cold, wet roots rather than cold alone. In the mildest zones you can leave it in the ground and mulch the crown heavily with straw or bark after the first hard frost.
What actually keeps mosquitoes away
If your real goal is fewer bites, set the magic-plant idea aside. The most effective protection is still a proven topical repellent, DEET remains the benchmark, with picaridin and oil of lemon eucalyptus as solid alternatives. Citronella oil (the real grass-derived kind) can help somewhat as a natural option, but it’s shorter-lived and weaker than DEET, so reapply often.
Beyond what you put on your skin, the highest-impact move is eliminating standing water where mosquitoes breed, empty saucers, buckets, clogged gutters, and birdbaths weekly. A strong box fan on the patio genuinely works, since mosquitoes are weak fliers. Many popular gadgets, by contrast, underdeliver: citronella candles and torches release only trace amounts of oil, and clip-on devices, ultrasonic “zappers,” and CO2 traps tend to disappoint in independent testing.
None of that diminishes the citronella geranium or the true citronella grass as plants. Grow the scented geranium for its lacy foliage, its bright lemon perfume, and its easygoing nature in a pot or border. Grow the grass if you want the genuine article and the option to distill or simply enjoy a dramatic tropical clump. Just buy them for what they are, fragrant, handsome, and rewarding, and reach for a real repellent when the mosquitoes show up.