Cymbopogon nardus (Citronella Grass)
Cymbopogon nardus (Citronella Grass)
Contents
Introduction & History
Citronella Grass is the aromatic powerhouse behind the world's most familiar natural insect repellent — the lemony scent of citronella candles, torches, and sprays comes from this tall, tropical grass. While less culinarily important than its cousin lemongrass, citronella grass is one of the most commercially significant aromatic plants, with global production of its essential oil running into thousands of tonnes annually.
History & Origin
Native to tropical Asia — Sri Lanka and Southeast Asia. Cultivated commercially since the 19th century for citronella oil production. Sri Lanka ('Ceylon citronella') and Indonesia ('Java citronella' — actually C. winterianus) are the major producing regions. The essential oil has been the primary natural mosquito repellent for over 150 years. Still grown on large commercial plantations across tropical Asia.
Botanical Description
Large, clump-forming tropical grass growing 120–200 cm tall — bigger than lemongrass. Leaves are long (up to 100 cm), blue-green, with a prominent red-pink base where they attach to the stem. The clumps are dense and fountain-like. The scent is strongly citrusy but harsher and less refined than lemongrass — more 'citronella' than 'lemon.' The stems are not as fleshy as lemongrass and are not used culinarily.
Stem: Semi-woody to woody at base • Height: 150 cm at maturity • Spread: 90 cm • Foliage: green-blue • Flowers: green (rarely)
Planting & Cultivation
Plant divisions or clumps in spring after all frost danger, spacing 90–120 cm apart — it's a big grass. Full sun, rich soil. In cold climates, grow in large containers (40+ litres). Less commonly available in nurseries than lemongrass. The reddish stem bases help distinguish it from lemongrass.
| Sun exposure | Full Sun |
| Soil pH | 5.5-7.5 |
| Spacing | 90 cm |
| Seed depth | 3–6 mm (surface-sow if light-dependent germinator) |
| Water needs | Moderate |
| Soil type | Well-drained, humus-rich loam; add perlite or grit for drainage |
Cultivation Details
Full sun, rich moist soil, and tropical warmth. Water freely during the growing season. Feed monthly. In temperate climates, grow as a summer annual or overwinter indoors. The larger size makes it more challenging in containers than lemongrass. In tropical gardens, it makes an impressive hedge or screen. The mosquito-repelling properties work best when leaves are crushed and rubbed on skin, not just from the plant's proximity.
Climate & Hardiness
Tropical — killed by frost. Root-hardy to about −3°C in zone 10 with heavy mulch. In all other zones, treat as a tender annual or container plant. Needs sustained heat above 20°C for vigorous growth. Less cold-tolerant than lemongrass.
USDA zones: 10-12
Minimum temperature: 3°C
Seasonal Care
Same as lemongrass. Spring: plant out after frost. Summer: peak growth. Autumn: harvest before frost; lift and store. Winter: in tropics, continues growing; in cold zones, dormant storage.
Propagation
By division of established clumps — the only practical method. Unlike lemongrass, grocery store stalks are not available. Purchase nursery plants or obtain divisions from growers. Seed is rarely available commercially.
| Method | Success rate | Time | Notes |
|---|---|---|---|
| Stem cuttings | 70–90% | 2—4 weeks | Softwood in spring, semi-ripe in summer; 8–12 cm |
| Division | 95%+ | Immediate | Split established clumps in spring or autumn |
| Seed | 50–80% | 14–28 days | Some require cold stratification; germination variable |
| Layering | 80–90% | 6–12 weeks | Pin low branch to soil; sever when rooted |
🌍 Distribution Map
Native origin: Sri Lanka, Southeast Asia
Diseases & Pests
Extremely pest-free — the citronella oil actively repels most insects. Rust possible in humid conditions. No significant pest problems. The plant's primary function is pest deterrence rather than being a pest target.
Culinary Uses
Not a culinary herb — the stems lack the fleshy, flavourful base of lemongrass and the essential oil profile is different (more citronellal, less citral). The leaves can flavour water or tea with a lemony note, but lemongrass is far superior for cooking. Citronella grass is grown for its repellent properties, not for the kitchen.
| Category | Pairing suggestions |
|---|---|
| Baking | Shortbread, scones, cakes |
| Preserves | Jelly, syrup, sugar |
| Cocktails | Gin botanicals, spritzers |
| Honey | Infused honey, dessert garnish |
Medicinal & Aromatherapy
The essential oil (citronellal, geraniol, citronellol) is the world's most widely used natural insect repellent. Also used in aromatherapy for its uplifting, refreshing scent. Traditional Sri Lankan medicine uses it for fever, digestive complaints, and as a general antiseptic. The oil has documented antifungal and antibacterial properties.
| Compound | Properties |
|---|---|
| linalool | floral, calming |
| cineole | camphoraceous, expectorant |
| thymol | antiseptic, warm |
| carvacrol | pungent, antimicrobial |
| eugenol | clove-like, analgesic |
Container & Companion Growing
Container Growing
Challenging due to the plant's large size (120–200 cm). Use 40+ litre containers. The tall, arching habit may overbalance smaller pots. In cold climates, container growing is the only option. Position on patios for mosquito-deterrent ambiance.
• Minimum pot size: 30–40 cm Ø, 15 L+
• Excellent drainage essential; add perlite
• Use free-draining potting compost with 20–30% perlite or grit
• Ensure drainage holes; stand on pot feet to prevent waterlogging
• Feed with dilute liquid fertiliser (half-strength) every 2–3 weeks in growing season
Companion Planting
Plant near outdoor seating areas, entrances, and windows for mosquito deterrence (though the repellent effect requires crushing leaves — the growing plant alone has limited range). Good hedge or screen in tropical gardens. Companion with lemongrass and ginger in tropical herb collections.
| ✓ Good companions | Roses, Brassicas, Fruit trees |
| ✗ Avoid planting with | Mint (invasive neighbour) |
Common Mistakes to Avoid
Expecting it to repel mosquitoes just by growing in the garden (it doesn't — you need to crush leaves to release the oil). Confusing it with lemongrass and trying to cook with it. Planting too small a container for its eventual size. Expecting it to survive any frost.
Harvesting & Preservation
Harvest leaves for fresh use — crush and rub on skin for insect repellent. The essential oil is extracted by steam distillation (commercial process). For home use, infuse crushed leaves in oil for a simple insect-repelling body oil. Dry leaves retain some fragrance for sachets. The plant's primary 'harvest' is its living presence as an insect deterrent.
• Time of day: Early morning, after dew has evaporated but before intense midday heat volatilises essential oils
• Growth stage: Just before flowering, when essential oil concentration peaks. Once flowers open, the plant redirects energy from leaf production
• Season: Year-Round
• Part harvested: Leaves
• Harvest rule: Never remove more than ⅓ of the plant at once; this ensures continued vigorous regrowth
• Technique: Cut stems cleanly above a leaf node with sharp scissors or secateurs. Tearing damages tissue and invites disease
| Method | Process | Shelf life | Best for |
|---|---|---|---|
| Air drying | Tie bundles, hang upside down in warm, dark, airy space | 6–12 months | Most herbs |
| Oven / dehydrator | Spread on trays, 35–45°C until crisp | 6–12 months | Fleshy-leaved herbs |
| Freezing (whole) | Blanch 5s, ice bath, pat dry, freeze flat on tray | 6 months | Basil, chives, parsley |
| Freezing (oil cubes) | Chop fine, pack into ice cube tray, cover with olive oil | 6 months | Any culinary herb |
| Herb salt | Layer herb and coarse salt 1:4, dry and grind | 12+ months | Rosemary, thyme, sage |
| Infused vinegar | Pack jar, cover with warm vinegar, steep 2–4 weeks | 6 months | Tarragon, dill, basil |
| Infused oil | Fill jar with dried herb, cover with oil, steep 4–6 weeks | 3–6 months | Rosemary, thyme, chilli |
Frequently Asked Questions
Does growing citronella grass repel mosquitoes?
The unbroken plant has minimal repellent effect — the oil must be released by crushing or bruising the leaves. Place crushed leaves around seating areas, or rub them on skin for personal protection. The commercial citronella products are concentrated oil, not just proximity to the plant.
Is it the same as lemongrass?
No — citronella grass (C. nardus) and lemongrass (C. citratus) are different species. Citronella has taller growth, red stem bases, and harsher scent. Lemongrass has fleshy culinary stalks and a sweeter, more refined lemon flavour. Citronella is for repelling; lemongrass is for eating.
Can I make my own citronella oil?
Basic infusions (crush leaves into carrier oil, steep for weeks) work for mild repellent use. True essential oil requires steam distillation equipment. For effective insect repellent, commercial citronella products are more reliable than homemade preparations.
Seasonal Care Calendar
🌱 Spring (Mar–May)
Water: Regular
Feeding: Regular feeding
☀️ Summer (Jun–Aug)
Water: Very Heavy
Feeding: Heavy feeding
🍂 Autumn (Sep–Nov)
Water: Regular
Feeding: Light feeding
❄️ Winter (Dec–Feb)
Water: Light
Feeding: No feeding
The source of citronella oil — the world's most popular natural insect repellent. Tall tropical grass (120–200 cm) with reddish stem bases. NOT the same as lemongrass and NOT for cooking. Frost-tender. Crush leaves to release repellent effect — growing alone has limited range.
Quick Reference: Cymbopogon nardus
Key Principles: Right location, well-drained soil, regular harvesting to promote growth, and appropriate winter protection for tender species.