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Citronella Plant: What It Is, and Whether It Repels Anything

The plant sold as citronella is a scented geranium, not the grass the oil comes from. What each one is, how to grow it, and the honest mosquito answer.

By Zakaria 4 min read Save to Pinterest — opens Pinterest in a new tab
A citronella scented geranium in a terracotta pot on a patio, showing deeply cut lacy foliage
Photo: Yercaud-elango, CC BY-SA 4.0, via Wikimedia Commons
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The plant sold as “citronella” is a scented geranium, the oil comes from a tropical grass, and the plant does not repel mosquitoes. All three facts are worth having before you buy one.

Three different plants, one name

What gets called citronella
PlantWhat it isHardy toSource of the oil?
Citronella geranium (Pelargonium)What shops sell. Lacy lemon-scented leaves, 2–3 ftZone 9No
Citronella grass (Cymbopogon nardus)Clumping tropical grass, 5–6 ftZone 10Yes
Citronella horsebalm (Collinsonia canadensis)North American woodland perennialZone 4No

The geranium is sometimes labelled Pelargonium citrosum or “Citrosa”, and marketed as the mosquito plant. It is a pelargonium crossed for scent, and the name is a commercial one rather than a botanical claim.

The mosquito question, answered honestly

Growing the plant does not protect you. The aromatic compounds are held inside the leaf tissue and released when the leaf is crushed or damaged — an intact plant sitting in a pot puts almost nothing into the air, and certainly not at a concentration that affects a mosquito.

This has been tested. Studies of the citronella geranium have found no meaningful reduction in mosquito landings on people near the plants.

What the evidence supports
ApproachDoes it work?
Growing citronella plantsNo measurable effect
Crushing leaves on skinBrief, mild, unreliable
Citronella oil on skinYes, but short-lived — reapply often
DEET or picaridinYes, and for hours
Oil of lemon eucalyptusYes, comparable to low-concentration DEET
Removing standing waterThe single most effective thing you can do
A fan on the patioSurprisingly effective — mosquitoes fly poorly

Standing water is the whole game

A mosquito needs about a week of standing water to go from egg to adult. That is a plant saucer, a blocked gutter, a bucket, a bird bath left unchanged, a fold in a tarpaulin, a child’s toy.

Tipping those out weekly does more than every repellent plant ever sold. It is also free.

None of this makes the plant not worth growing. It is a good-looking, tough, aromatic pelargonium that smells wonderful when you brush past it. Buy it for that.

Growing the geranium

It is a pelargonium, and the commonest way to kill one is kindness with the watering can.

Care
SunFull — 6+ hours
SoilGritty and free-draining. Add perlite or grit to standard compost
WaterOnly when the top inch is dry. It rots before it wilts
FeedLight, low-nitrogen, through summer only
Size2–3 ft, spreading
HardinessZone 9. Frost kills it
  • Pinch the growing tips when young, or it goes leggy and sparse
  • Deadhead the small mauve-pink flowers to keep it tidy; they are not the point of the plant
  • Overwinter indoors — bright, cool, barely watered, and cut back hard in spring
  • Cuttings root easily in late summer, which is the cheap way to keep it going year to year

Toxic to dogs and cats

Like other pelargoniums, the citronella geranium is on the ASPCA’s toxic list for dogs, cats and horses — vomiting, loss of appetite, skin irritation.

It is sold specifically for decks and patios, which is exactly where pets sit on summer evenings. Worth placing out of reach, or choosing something else if you have a chewer.

Growing citronella grass

If you want the actual plant the oil comes from:

  • Full sun and heat; it is tropical and wants both
  • Steady moisture — the opposite of the geranium
  • Rich soil, and a generous feed through summer
  • 5–6 ft tall in a good season, clumping
  • Zone 10. Grown as an annual or a large container plant everywhere else, brought in before frost

It is closely related to lemongrass and looks much the same. Unlike the geranium, the leaves are genuinely the commercial source of citronella oil — though extracting anything useful at home is not realistic.

Common questions

What is the citronella plant?

Almost always a scented geranium — a Pelargonium sold as the citronella plant or mosquito plant, with lacy lemon-scented leaves. It is not the source of citronella oil. That comes from citronella grass, Cymbopogon nardus and Cymbopogon winterianus, tall tropical grasses that look nothing like a geranium. A third plant, Collinsonia canadensis, also carries the name in North America. The geranium is what garden centres stock, and the confusion is largely a marketing one.

Does the citronella plant actually repel mosquitoes?

Not as a growing plant, no. Controlled studies of the citronella-scented geranium have repeatedly found no meaningful reduction in mosquito landings from having one nearby, because the aromatic compounds stay inside the leaf until it is crushed and never reach a useful concentration in open air. Citronella oil applied to skin does repel mosquitoes, but for a much shorter time than DEET or picaridin. Crushing leaves and rubbing them on skin gives brief, mild and unreliable protection.

How do you care for a citronella geranium?

Treat it exactly as a pelargonium: full sun, gritty free-draining compost, and water only when the top inch has dried, because it rots far more easily than it wilts. Feed lightly through summer with a low-nitrogen feed, pinch the tips to keep it bushy, and expect a plant 2 to 3 feet tall. It is hardy only to about zone 9, so in colder regions bring it in before frost, keep it cool and bright and barely watered over winter, then cut it back in spring.

Is citronella grass the same plant?

No, and it is the one the oil actually comes from. Citronella grass is Cymbopogon nardus or Cymbopogon winterianus, a clumping tropical grass reaching 5 to 6 feet, closely related to lemongrass and hardy only to zone 10. It needs full sun, heat, and steady moisture — the opposite of the geranium's preference for dry feet — and it is grown as an annual or a large pot plant anywhere with frost.

Is the citronella plant toxic to pets?

The citronella geranium is listed as toxic to dogs, cats and horses by the ASPCA, like other pelargoniums, causing vomiting and skin irritation. Citronella oil itself is also an irritant and should not be applied to pets. This is worth knowing precisely because the plant is marketed for patios and decks, which is exactly where pets spend summer evenings.

What actually works against mosquitoes in a garden?

Removing standing water, because mosquitoes breed in anything holding water for about a week — saucers, gutters, buckets, bird baths, tarpaulin folds. After that, a fan on a patio is remarkably effective since mosquitoes are weak fliers, and a repellent containing DEET, picaridin or oil of lemon eucalyptus works on skin. Planting anything, including citronella, is the least effective of the options despite being the most marketed.

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