Every spring, garden centers across the Carolinas fill a table with "mosquito plants": citronella geraniums, lemongrass, lavender, marigolds, rosemary. People line the patio with them and still get bitten. That isn't bad luck. Researchers have now tested these plants in real yards, and the results are clear.
No plant keeps mosquitoes out of your yard just by growing there. In a 16-week field trial published in 2026, potted citronella-scented geraniums and rosemary did not reduce the number of mosquitoes caught next to them, even when the leaves were cut up every week to release their oils. An older field test of the citrosa "mosquito plant" found the same thing.
Some plants do contain real repellent compounds, but only when the leaves are crushed and rubbed on skin, and then the protection lasts minutes. What actually works in a Carolina yard is dumping standing water, using an EPA-registered repellent, running a fan, and treating the shrubs where mosquitoes rest.
What the Research Found
Most "mosquito-repelling plant" lists are written from the fact that a plant contains a repellent oil. The question that matters is whether the living plant, sitting in your yard, keeps mosquitoes away. That has now been tested directly.
| Study | What was tested | Result |
|---|---|---|
| Sacramento-Yolo Mosquito and Vector Control District, Journal of Medical Entomology, 2026 | Six popular plants screened in the lab. The top two, citronella-scented geranium and prostrate rosemary, were then tested in urban and rural yards for 16 weeks. That came to 44,527 mosquitoes caught, including the yellow fever mosquito | Neither plant reduced mosquito catches compared with no plants, whether the plants were left alone or trimmed every week to release their oils. A metofluthrin repellent device did reduce catches |
| Matsuda and colleagues, Journal of the American Mosquito Control Association, 1996 | The citrosa "mosquito plant" placed around people outdoors | No significant difference in bites compared with no plant. A 75% DEET repellent cut bites by more than 90% for up to 8 hours |
| Review of 62 studies on plant-based repellents, Malaria Journal, as summarized by Clemson Extension | Plant oils tested against mosquitoes | 56 of the 62 studies were done in a lab. Only 6 were in the field, and none tested landscape plantings |
Clemson Extension's Home and Garden Information Center sums up why: the scent a plant gives off dissipates into the air, and a breeze minimizes it. To work as a repellent, a plant's leaves have to be crushed or its oil rubbed directly on skin. Clemson notes that in testing, rosemary oil protected people for about 15 minutes and lemongrass oil for about 40. Clemson's own advice is that the best way to control mosquitoes is source reduction and chemical control, not plants.
The Popular "Mosquito Plants," One by One
| Plant | What's in it | Does the growing plant repel mosquitoes? | Worth growing? |
|---|---|---|---|
| Citronella-scented geranium (citrosa) | Geraniol, citronellol. It smells like citronella but is a geranium, not the source of citronella oil | No. Failed field tests in 1996 and 2026 | As a fragrant plant, yes. Toxic to dogs and cats (ASPCA) |
| Citronella grass / lemongrass | Citronellal and related oils. The true source of citronella oil | No evidence. Lemongrass was screened in the 2026 study and was not chosen for field testing | Yes, as an ornamental grass or for cooking |
| Lavender | Linalool | No evidence. Screened in the 2026 study | Yes, but it needs sharp drainage in Lowcountry humidity |
| Rosemary | Camphor, eucalyptol | No. Failed the 2026 field test | Yes, a tough evergreen herb for the Carolinas |
| Marigolds | Thiophenes and other compounds | No evidence. They do not contain pyrethrum, despite what many lists say | Yes, as bright summer annuals |
| Basil | Linalool, eugenol | No field evidence | Yes, for the kitchen |
| Catnip | Nepetalactone | The distilled oil is a strong repellent in the lab, but no field evidence for the living plant | Yes, but expect cats to roll in it |
| American beautyberry (native) | Callicarpenal, intermedeol | Crushed leaves repel mosquitoes in USDA testing. Not tested as a planting | Yes. A native shrub that feeds birds |
Two myths on those lists need correcting. First, marigolds are not a source of pyrethrum. The National Pesticide Information Center explains that pyrethrins, the natural insecticides used in many mosquito products, come from the flowers of a chrysanthemum, Chrysanthemum cinerariaefolium. Second, the "catnip is ten times stronger than DEET" claim comes from Iowa State University lab work on distilled catnip oil in a test chamber, not from catnip plants in a garden. A 2021 study in Current Biology later showed why the oil works: it triggers an irritant receptor in insects that it doesn't trigger in people. Neither study shows that a catnip plant on the patio keeps mosquitoes away.
Native Plants and Mosquitoes in the Carolinas
If you want a native plant with a real mosquito story, it is American beautyberry (Callicarpa americana), common in woods and yards from the Lowcountry to the Upstate. In northeastern Mississippi, people rubbed its crushed leaves on themselves and their farm animals to keep biting insects off. The University of Mississippi described it as a folk remedy known in the state's hill country for at least a century.
USDA Agricultural Research Service and University of Mississippi scientists tested that tip. They isolated three repellent compounds from the leaves: callicarpenal, intermedeol and spathulenol. They confirmed the crushed leaves repel mosquitoes, including the species that carry yellow fever and malaria, and found that callicarpenal also repelled blacklegged ticks. That is real science behind a native plant, but it is about crushed leaves on skin. Nobody has shown that a beautyberry hedge keeps mosquitoes out of a yard, so be skeptical of landscapers who sell it as a "natural barrier."
One planting result from Africa is worth knowing about. In a 2011 study in Tanzania, planting lantana around houses cut the number of mosquitoes indoors by about half. That suggests a thick screen of plants around a house can change how many mosquitoes come in. But lantana is toxic to dogs, cats and horses according to the ASPCA, and is listed as an invasive plant in Florida, so we don't recommend planting it for mosquitoes.
The bigger native-plant lesson in the Carolinas is about water. Clemson Extension's fact sheet on the Asian tiger mosquito, the main daytime biter in our yards, lists flower pots, birdbaths, clogged gutters and tree holes among its breeding sites. It goes from egg to biting adult in about a week. Plant saucers that hold rainwater, tank bromeliads and soggy beds can breed more mosquitoes than any plant could ever repel.
What Gardeners Report
We read through a long Houzz thread from Southeast coastal gardeners and the Reddit gardening threads Google surfaces for this question (Reddit blocks automated reading, so we worked from Google's excerpts). The pattern matches the research.
| What people described | Reports | What the research says |
|---|---|---|
| Planted citronella geraniums, lemongrass, lemon basil or lemon thyme and still got bitten. "They smell great, I still have mosquitoes" | About 8 | Matches the field trials: no measurable effect from living plants |
| Plants seemed to help, but only right next to them. "Walk a few feet away and they got you" | About 4 | Any effect is very local and short-lived, and these reports aren't controlled |
| Rubbing crushed leaves (citronella geranium, beautyberry) on skin worked for a while | 2 | Consistent with the research on crushed leaves and oils. Protection lasts minutes |
| Citronella oil only works with "absolutely no breeze" | 1 | Matches Clemson: scent dissipates and wind removes it |
| Mosquito dunks in standing water or a DEET repellent worked best | 3 | Matches extension advice: source reduction and registered repellents |
One safety note from that thread: a gardener rubbed crushed citronella geranium leaves on a cat to keep mosquitoes off it. The ASPCA lists scented geraniums as toxic to cats and dogs because of the same oils, geraniol and linalool, that give them their scent. Don't use plant leaves or essential oils on pets.
What Actually Keeps Mosquitoes Off You in a Carolina Yard
- Dump standing water every week. Tip plant saucers, birdbaths, buckets, toys, tarps and anything that holds water, and clean gutters. For water you can't dump, such as a pond or rain barrel, Clemson recommends Bti mosquito dunks, a bacterial product that kills the larvae.
- Wear an EPA-registered repellent. The CDC recommends DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), PMD or 2-undecanone. In head-to-head tests at New Mexico State University, sprays with DEET and PMD performed best, and a citronella candle had no effect. Don't use OLE or PMD on children under 3.
- Use the right lemon eucalyptus. The CDC-recommended "oil of lemon eucalyptus" is a refined, EPA-registered product. It is not the same as the essential oil sold for aromatherapy, and not the same as rubbing leaves from a lemon eucalyptus tree.
- Run a fan on the patio. Mosquitoes are weak fliers, and moving air makes it much harder for them to reach you.
- Treat where they rest. Adult mosquitoes rest in shady shrubs and ground cover. In an NC State study of Asian tiger mosquitoes in suburban yards, a barrier spray on that vegetation significantly reduced mosquitoes, and adding standing-water cleanup made the treatment work better as the weeks went on.
Plant herbs and flowers because you like them. Just don't count on them for mosquito protection. If mosquitoes are taking over your evenings, our mosquito control service treats the resting areas around your yard monthly through the season and points out breeding sites on every visit. For timing, see how often to spray for mosquitoes in the South.
Key Takeaways
- Living plants don't repel mosquitoes from a yard. Citronella geranium and rosemary failed a 16-week field trial in 2026, even when trimmed to release their oils.
- Crushed leaves can work briefly on skin, roughly 15 to 40 minutes for rosemary and lemongrass oils, according to Clemson.
- American beautyberry is the native plant with real research behind its crushed leaves, but not as a hedge or barrier.
- Marigolds don't contain pyrethrum, and the catnip "10 times DEET" result came from distilled oil in a lab.
- Scented geraniums and lantana are toxic to pets.
- What works: dump standing water weekly, wear an EPA-registered repellent, run a fan, and treat the shrubs where mosquitoes rest.
Sources: M. Novelo, J. Brodigan, W. Clack, T. Fowles and S. S. Wheeler, "Evaluation of 2 ornamental plants, Citronella-Scented Geranium and prostrate rosemary, for spatial repellency of host-seeking mosquitoes", Journal of Medical Entomology 63(4), 2026; Matsuda, Surgeoner and colleagues, "Essential oil analysis and field evaluation of the citrosa plant 'Pelargonium citrosum' as a repellent against populations of Aedes mosquitoes", Journal of the American Mosquito Control Association 12 (1996); J. Jordan, "Can Plants Repel Problematic Insects?", Clemson Cooperative Extension, 2025; W. K. Reeves, E. P. Benson and C. Stoops, "Asian Tiger Mosquito" (HGIC 2471), Clemson Cooperative Extension; C. J. Peterson and J. R. Coats, "Catnip Essential Oil and Its Nepetalactone Isomers as Repellents for Mosquitoes", Iowa State University, 2001; N. Melo et al., "The irritant receptor TRPA1 mediates the mosquito repellent effect of catnip", Current Biology 31 (2021); USDA Agricultural Research Service, "Old-Time Mosquito Remedy May Work Against Ticks, Too", 2007; University of Mississippi, "Scientists Confirm Folk Remedy Repels Mosquitoes", 2006; F. C. Mng'ong'o et al., "Repellent Plants Provide Affordable Natural Screening to Prevent Mosquito House Entry in Tropical Rural Settings", PLoS One, 2011; National Pesticide Information Center, "Pyrethrins General Fact Sheet"; ASPCA Animal Poison Control, scented geranium and lantana entries; Centers for Disease Control and Prevention, "Preventing Mosquito Bites"; S. D. Rodriguez et al., "The Efficacy of Some Commercially Available Insect Repellents for Aedes aegypti and Aedes albopictus", Journal of Insect Science 15 (2015), and "Efficacy of Some Wearable Devices Compared with Spray-On Insect Repellents", Journal of Insect Science 17 (2017); B. Hollingsworth, P. Hawkins, A. L. Lloyd and M. H. Reiskind, "Efficacy and Spatial Extent of Yard-Scale Control of Aedes albopictus Using Barrier Sprays and Larval Habitat Management", Journal of Medical Entomology 57 (2020); owner accounts from the Houzz Southeast Coastal Gardening forum and Reddit (via Google search excerpts).
Frequently Asked Questions
Not as living plants in a yard. In a 16-week field trial published in 2026, potted citronella-scented geraniums and rosemary did not reduce mosquitoes around them, even when the leaves were trimmed weekly. Some plants contain repellent oils, but they only work when the leaves are crushed and rubbed on skin, and then only for minutes.
No. The plant sold as a citronella or mosquito plant is usually a citronella-scented geranium. It failed field tests in 1996 and again in 2026. Citronella oil itself comes from a grass, and even citronella candles had no measurable effect in New Mexico State University testing.
American beautyberry is the native plant with real research behind it. USDA scientists found that its crushed leaves contain compounds, including callicarpenal, that repel mosquitoes and ticks. That works for crushed leaves on skin. No study shows a beautyberry planting keeps mosquitoes out of a yard.
There is no good evidence that a lavender plant repels mosquitoes. Lavender was one of six plants screened in a 2026 study, and it did not make the cut for field testing. Grow it for its looks and scent, not for mosquito control.
There's no evidence they do. Marigolds are often said to contain pyrethrum, but pyrethrins come from chrysanthemum flowers, not marigolds, according to the National Pesticide Information Center.
Distilled catnip oil was a stronger spatial repellent than DEET in Iowa State University lab tests, which is where the '10 times stronger' claim comes from. That was concentrated oil in a test chamber. A catnip plant in your garden does not give you that protection.
The scents with the best evidence are the EPA-registered repellents the CDC recommends: DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD and 2-undecanone. Plant scents work only briefly, if at all, once they drift into open air.
There is no evidence that coffee grounds repel adult mosquitoes. Lab studies have found that used coffee grounds and caffeine in water can stop mosquito larvae from developing, but dumping the water does the same job more reliably.
Not all of them. The ASPCA lists scented geraniums, including the citronella geranium, and lantana as toxic to dogs and cats. Don't rub plant leaves or essential oils on pets to keep mosquitoes off them.
Dump standing water every week, including plant saucers, birdbaths and gutters. Wear an EPA-registered repellent, run a fan on the patio, and treat the shrubs and ground cover where adult mosquitoes rest. In an NC State yard study, a barrier spray significantly reduced Asian tiger mosquitoes.
Photo credits: Chhe, public domain, via Wikimedia Commons; Alex Abair, CC BY 4.0, via Wikimedia Commons; James Gathany, CDC, public domain.