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Pelargonium 'citrosum'
Caution🐾Citronella-Geranie · (Pelargonium citrosum)
Cranesbill family (Geraniaceae)
Description
The citronella geranium is a horticultural hybrid with deeply cut foliage, small pink-violet flowers and a lemon-rose scent released when the leaves are touched. It became widely known under trade names such as mosquito plant. That promise, however, does not hold: a controlled field study by Matsuda and colleagues in 1996 found no meaningful protection against biting mosquitoes — the plant is fragrant, but it does not repel. As a scented container plant it nonetheless remains tough, easy to keep and valued in sensory and fragrance gardens, precisely because its aroma has to be coaxed out by touch. The leaves make a light, lemony tea for pleasure; there is, by contrast, no industrially distilled citrosum oil. Take care with skin: citronellol and geraniol count as allergens, and crushed leaves do not belong on irritated or broken skin.
Folk belief and marketing claim: the hybrid sold as 'citronella geranium', 'mosquito shocker' or 'mosquito plant' is marketed as an allegedly mosquito-repelling potted plant. SCIENTIFICALLY DISPUTED: the controlled field study by Matsuda et al. (1996, Journal of the American Mosquito Control Association) showed that P. citrosum offered no better mosquito protection than a control pot — mosquito landings were statistically equivalent. Tisgratog et al. (2016) confirmed this for Aedes mosquitoes. The intact plant releases too little volatile geraniol/citronellol to act as a repellent; only a crushed leaf rubbed directly on the skin produces a very weak, locally confined, short-lived effect. The plant nonetheless remains a popular hobby-garden element — as a scented plant, not as a reliable mosquito shield.
Preparation & dosage
⚠ Age restriction: ≥ 2 years — No skin contact with crushed pelargonium leaves in children under 2 years — citronellol and geraniol are potent skin allergens.
Scented-garden plant: despite the disproven mosquito advertising claims, the citronella geranium is an attractive, robust potted plant with citrus-rosy leaf scent, small pink-violet flowers and attractively dissected foliage. Valued in sensory and scented gardens for the haptic experience (scent release on touch) and as a low-maintenance balcony or windowsill plant. Suitable for therapy and dementia gardens, since brushing the leaves produces olfactory stimulation.
Folk practice (rare, weakly documented compared to P. graveolens and P. odoratissimum): infusion of fresh leaves as a light, citrus-rose-scented pleasure tea. The aroma resembles a mix of citronella grass and rose geranium. Because of the comparatively recent hybrid history (commercially from the 1980s onward), there is no traditional herbal-medicine use — the application is purely modern and recreational.
Preparation & dosage
Pour 200 ml boiling water over 1-2 g (2-3 fresh or 1 tsp dried) chopped citronella geranium leaves, cover and infuse for 8 minutes, then strain. 1-2 cups daily. Fresh leaves give a markedly stronger aroma than dried.
- Dry amount
- 1–2 g
- Doses per day
- 2×
- Max duration
- 4 weeks
Folk aromatherapy use: crushed fresh leaves or a homemade infused-oil maceration emit a citrus-rosy scent considered relaxing and mood-lifting in hobby aromatherapy. Important: there is no industrial steam-distilled genuine 'P. citrosum' oil on the market — commercial geranium oils come from P. graveolens or P. capitatum. The effect is very mild compared to true geranium Bourbon oil.
Preparation & dosage
⚠ Age restriction: ≥ 6 years — In children under 6 years, avoid intensive use due to citronellol/geraniol content. Avoid entirely in infants and toddlers.
NEVER apply crushed leaves of citronella geranium to irritated or broken skin — citronellol and geraniol are listed allergens (declarable fragrance allergens in the EU Cosmetics Regulation) and can cause contact dermatitis on repeated exposure. Patch test 24 h before first use. IMPORTANT — scientific honesty: the commercial marketing as 'anti-mosquito plant' or 'mosquito shocker' has been REFUTED by two controlled studies (Matsuda et al. 1996; Tisgratog et al. 2016) — the intact plant has no significant mosquito-repellent activity. Anyone relying on dependable mosquito protection (travel in malaria or dengue zones, sensitive individuals) MUST use certified repellents such as DEET, icaridin or IR3535. A citronella geranium on the terrace does not replace effective mosquito protection. Additionally: the EMA HMPC pelargonium monograph refers EXCLUSIVELY to Pelargonium sidoides (respiratory colds); there is NO EMA monograph and no 'well-established use' status for P. citrosum. ASPCA classification (accessed 2026-08-10): toxic to dogs and cats. The ASPCA classifies the whole genus this way.
⏱ Max continuous use: 4 weeks
Culinary amounts (e.g. occasional leaves in tea) are considered safe. Avoid infused skin oils and intensive skin contact with crushed leaves during pregnancy due to insufficient safety data. Avoid internal use of essential oil.
Culinary amounts are safe. Use infused oils and skin applications cautiously due to insufficient data; do not apply oils to chest or nipples while breastfeeding.
Do NOT use crushed citronella geranium leaves and infused oils on the skin of infants and children under 2 years. In children 2-6 years only highly diluted (max. 0.5 %) and not on the face. Critically: do NOT use as an alleged mosquito repellent on children in risk areas — only paediatrically approved repellents (icaridin 10 %, IR3535) should be used there.
Drug interactions
CYP2B6-/CYP3A4-Substrate
Citronellol, geraniol and linalool can modulate cytochrome P450 enzymes (especially CYP2B6) at higher concentrations. Theoretical interactions with bupropion, efavirenz, ketamine and other CYP2B6 substrates are conceivable — barely clinically relevant for topical aromatherapy, caution with oral use of essential oils.
Contraindications
- Known hypersensitivity to pelargoniums, citronellol, geraniol, linalool or other Geraniaceae.
- Infants and children under 2 years — no skin contact with crushed leaves or infused oils.
- Travel to malaria, dengue or Zika risk areas: the citronella geranium is NOT an approved repellent and MUST NOT replace certified mosquito repellents (DEET, icaridin, IR3535). Relying on the plant constitutes a medical risk.
- Acute weeping skin inflammation or irritated mucous membranes — postpone use until healed.
- Cats and small dogs in the household: geranium essential oils are toxic to pets (per ASPCA — applies to all Pelargonium species). No direct application on the pet; diffusers only in rooms the animal can leave.
Harvested part: leaves (crushed)
- Time of day:
- Early morning in dry weather once the dew has dried and before midday heat — essential-oil content is then highest. Prefer non-flowering, strong shoot tips; young leaves are more aromatic than older ones.
- Drying:
- Spread leaves and leafy shoots in a thin layer on cloths or mesh racks in a warm, airy, shaded room (max 35 °C). Avoid direct sunlight — the citrus-rose scent is otherwise quickly lost. After drying, store airtight in dark glass jars.
- Storage:
- 6 months — Store in dark, tightly closed glass or tin containers, cool and dry. Aroma evaporates quickly — use within 6 months, fresh material is markedly more potent.
- Ätherisches Öl (Citronella-Geranien-Öl)Essential oilContent: 0.05-0.15 %Leaf
Steam distillate from fresh leaves — practically unavailable commercially. Yield markedly lower than P. graveolens (Bourbon oil). Profile: citrus-rosy with pronounced citronellol and geraniol note but at lower concentration. Hybrid genealogy is disputed; presumed cross of P. graveolens with P. spec. carrying an elevated citral fraction.
- citronellolEssential oilContent: 15-30 %Leaf
Monoterpene alcohol — main component. Proportion slightly lower than in classical geranium Bourbon oil (P. graveolens, 20-40 %). Responsible for the rose-citrus base and a weak, locally confined mosquito-repellent effect (only when released from crushed leaves). EU-declarable fragrance allergen.
- geraniolEssential oilContent: 5-15 %Leaf
Second leading substance. Sweet rosy scent, antioxidant, antimicrobial and mildly anti-inflammatory; theoretically repellent against mosquitoes — but the intact plant releases too little geraniol into the surrounding air to deter mosquitoes (Matsuda 1996). EU-declarable allergen.
- linaloolEssential oilContent: 3-10 %Leaf
Monoterpene alcohol with calming, mildly anxiolytic effect — typical accompanying compound in citronella geranium oil. EU-declarable fragrance allergen.
- citral (geranial + neral)Essential oilContent: 1-5 %Leaf
Aldehyde mixture — responsible for the citrus top note that distinguishes P. citrosum from the rosier P. graveolens and the apple-like P. odoratissimum. Far more concentrated in citronella grass (Cymbopogon nardus); only present in small amounts in P. citrosum. Known fragrance allergen and mildly skin-irritating on direct contact.
- beta-caryophylleneSesquiterpeneContent: 1-4 %Leaf
Sesquiterpene with anti-inflammatory action and affinity for the CB2 receptor of the endocannabinoid system. Contributes a mildly spicy-woody note to the scent profile.
- citronellyl formateEssential oilContent: 2-6 %Leaf
Ester accompanying compound — gives the oil a fruity-floral top note. Contributes to the relaxing effect of crushed leaves in hobby aromatherapy.
- Gerbstoffe (kondensierte Gerbstoffe)TanninContent: 2-4 %Leaf
Astringent polyphenols — typical of Pelargonium leaves; contribute to the mildly puckering effect of aqueous extracts. In P. citrosum from hybrid genealogy somewhat lower than in the purer P. graveolens.
- [1]MonographMatsuda B.M., Surgeoner G.A., Heal J.D., Tucker A.O., Maciarello M.J. (1996) — 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(1): 69-74.(accessed: 2026-05-27)
- [2]MonographTisgratog R., Sanguanpong U., Grieco J.P., Ngoen-Klan R., Chareonviriyaphap T. (2016) — Plants traditionally used as mosquito repellents and the implication for their use in vector control. Acta Tropica 157: 136-144.(accessed: 2026-05-27)
- [4]MonographPlants For A Future — Pelargonium citrosum (Citronella geranium / Mosquito plant)(accessed: 2026-05-27)
- [5]MonographU.S. Centers for Disease Control and Prevention (CDC) — Mosquito Bite Prevention for Travelers (recommended EPA-registered repellents: DEET, picaridin/icaridin, IR3535, oil of lemon eucalyptus)(accessed: 2026-05-27)
- [6]MonographRoyal Horticultural Society (RHS) — Pelargonium 'Citrosa' / Citronella-scented geranium cultivar profile(accessed: 2026-05-27)
- [7]MonographLalli J.Y.Y., Viljoen A.M., Baser K.H.C., Demirci B., Oezek T. (2008) — The essential oil composition and chemotaxonomical appraisal of South African Pelargoniums (Geraniaceae). Journal of Essential Oil Research 20(2): 152-160.(accessed: 2026-05-27)
- [8]MonographASPCA Animal Poison Control — Geranium (Pelargonium species)(accessed: 2026-08-10)
- [3]WikipediaPelargonium 'citrosum' (Wikipedia EN)(accessed: 2026-05-27)
Distribution in Europe
🪴 Grow at home
- ☀ Light
- full sun
- 💧 Water
- every few days
- 🌱 Soil
- Geranium compost
- 🪴 Pot
- 20 cm
- ⭐ Difficulty
- ★☆☆ beginner
- 🐾 Pets
- toxic to pets
Tips:
- Effect is strongest when leaves are touched or crushed.
- Place on balcony table or seating area for dining mosquito repellent.
- Winter: bright and cool (5-12 °C).
Care tips are general indoor-gardening recommendations, not scientific sources.