How to Plant, Grow, and Care for Citronella

Citronella oil – the savior in the battle against the mighty mosquito! If you live in a warm, humid climate, you will have heard of citronella oil. It is used in a burner, as a candle, or a cosmetic lotion smothered on the skin to repel mosquitoes from biting. But do you know where it comes from? Well, let me introduce you to citronella: Cymbopogon nardus!

Citronella is not to be confused with another lemony ‘supposed’ insect repellent plant, the scented geranium, Pelargonium citrosum (or Citrosa geranium). The scented geranium, sometimes called citronella geranium, is easy on the eye and smells wonderful. Unfortunately, it does nothing in the battle against pests.

The true citronella is a large tufted perennial grass with green leaves growing upright to six feet tall and four feet wide in the right conditions. It’s the oil contained within the leaves that repel insects, and it can only be harvested by crushing the leaves. The existence of these grasses, with their medium green texture alone, will not deter mosquitos. 

The oil has a long history of medicinal use, such as treating lice, parasites, or worms and relieving migraines and fevers. Its antibacterial, antimicrobial, anti-inflammatory, and anti-fungal properties make it useful in both cleaning and cosmetic products, providing them with an unmistakable lemon scent. Planting it is a great way to add several contrasting textures to your garden.

What is Citronella?

If you find a plant at garden centers or big box stores with the botanical name Cymbopogon nardus or Cymbopogon winterianus then you can be confident you have discovered the commonly known citronella, also known as citronella grass, geranium grass, mosquito plant, and nardus grass. It comes from the plant family Poaceae.

Native Area

Cymbopogon nardus is an aromatic evergreen perennial native to Sri Lanka but common in most warm-temperate, subtropical, and tropical regions of Asia and Africa. 

Cymbopogon winterianus is very similar and from the same family but originates in Borneo, Java, and Sumatra. It is commonly referred to as Java citronella.

Characteristics

In cooler climates, grow as annuals and bring indoors over winter. It’s closely related to lemon grass. This grass is an upright tufted grass with lance-shaped bluish-green leaves sprouting from long brownish-red erect stems.

When optimum conditions are met for growing, citronella will produce panicles of flowers on spikelets borne on long flowering stems protruding up to six feet from the center of the plant.  These flowers will readily self-seed but require consistent temperatures of between 68-72°F (20-21°C) to germinate. Seeds are light brown, dry, and typical of grasses/cereals. Those grown in cooler climates are less likely to produce viable flowers. 

Citronella will spread naturally through creeping underground rhizomes and can become somewhat invasive in their natural tropical climate with their vigorous growing habit, out-competing existing flora and cultivated crops.

This grass is typically grown in a summer border or window boxes for its insect-repellent properties. Many gardeners believe that the citrus aroma of plants is enough to repel mosquitos like bug zappers, but unfortunately, this is not true. 

Planting

Plant throughout the year if grown in tropical, subtropical, or warm temperate climates. The vigorously growing grass won’t take long to establish. In cooler climates wait until late spring to early summer before planting out into the garden.   

Choose a location in full sun with some partial shade in the hottest part of the day. Leaves can become easily scorched and look unsightly. This grass is adaptable to most soil types, but it prefers moist loam-based soil that is well-draining.

Growing from seed is not recommended as germination can be erratic. However, the vigorous growth and rhizomatic roots make it a prime candidate for propagation from division. 

Citronella grass is perfect for growing as potted plants as it allows you to move it into a variety of locations to suit your needs. You may need to invest in larger pots as your container plants outgrow smaller containers or simply divide and replant a division in the same container and share the others with fellow gardeners. Container growing is a good option for colder zones as it allows your grass to be easily moved indoors over winter to protect it from frost. 

How to Grow

This grass is native to the tropics. However, it is very adaptable to cooler climates if you know how to look after it. Let’s talk about the information you’ll need to know to care for them and maintain their lovely foliage in your garden!

Light

Citronella is primarily a subtropical grass that prefers full sun (at least six hours) and warm temperatures. In very hot climates, provide shade or filtered sunlight during the hottest time of the day to prevent the leaves from scorching. Make certain it gets at least six hours of sunlight. In areas with less heat, give it more light.

Water

Provide long deep drinks when the soil begins to dry out or provide irrigation through soaker/drip hoses to maintain consistent moisture. This grass prefers consistently moist soil but surprisingly can tolerate long periods of drought. Reduce watering during the winter months but check regularly to ensure plants have not completely dried out, especially those grown in containers.

Soil

For optimum results, grow citronella in a rich loam-based, free-draining soil or compost. Citronella is very adaptive to most soil types and will do well once established. Where soils are very poor, dig in some organic matter before planting to provide nutrients and help with moisture retention. Soil pH should be neutral, and well-drained soils are best.

Temperature

Don’t let this plant’s tropical origins put you off growing it if you are located north of the equator!  Hardy to USDA zones 10-12, citronella can tolerate temperatures down to 32°F (0°C) but will not tolerate prolonged periods of frost. Bring your citronella indoors in large pots when the first frost is forecast.

Fertilizing

Fertilize citronella once a year in spring with a good-quality, slow-release nitrogen-rich fertilizer. If your grass is looking a little lackluster, then a quick feed with a liquid nitrogen fertilizer or all-purpose food should bring it back to healthy growing habits. Adding a top inch of compost once or twice a year around the base will also work in lieu of fertilizers or all-purpose food.

Maintenance

Citronella require little or no pruning when grown in their natural environment. At most, perhaps they can benefit from the odd trim of brown leaves and deadheading every few weeks to prevent self-seeding. If grown in containers in cooler climates, they will benefit from a hard prune to six inches above the crown before bringing them into a sheltered area or indoors over winter. New shoots will appear in spring ready for going back outside.

Propagation

This grass is unlikely to develop viable seeds unless grown in optimum climate conditions.  Even with viable seeds, germination is erratic. The main form of propagation for citronella is via division. The vigorous growing nature of citronella lends itself perfectly to division to keep it’s size under control.  It’s also a great way to keep container-grown grasses in check.

Divide a healthy grass that is at least two to three years old and has developed a good root system. Dig up the entire grass, and using a saw, spade, or knife, divide it into as many divisions as you require. Pot each division up individually or replant into new positions in the garden. Water well until they are established. If using this method, make sure there’s ample time for the new citronella to become well-established before the first frost.

Root cuttings are another option if you don’t wish to dig up an entire grass. Root cuttings should be taken in winter when they are dormant, and their roots are nutrient-rich, thus giving cuttings the best chance to develop. Simply remove soil from the base until roots are visible and cut off two to three inches of root with a clean pair of snips. Place the cutting into a pot of compost and place it somewhere bright and warm, keeping the compost moist. Shoots should appear in early spring.

Harvesting

The oil contained within the leaves is used in mosquito repellents, but it must be extracted first through the process of distillation. If you simply crush the leaves by hand, you will release some oil, but it is not enough to repel mosquitoes. Nonetheless, some gardeners swear that crushing and rubbing the leaves on their skin is one of the natural ways to apply a mosquito repellent and that citronella scent may be successful in keeping a few mosquitoes away while you’re working in the garden! Best to pair them with bug zappers for best results.

The extracted essential oil of citronella mosquito plants has a strong lemony fragrance often used to perfume cosmetics, soaps, deodorants, and skin lotions specifically used as mosquito repellents. Citronella candles and oil burners are used at night as a mosquito repellent. The anti-bacterial and anti-fungal nature of the oil makes it perfect for cleaning and disinfecting products. 

Use caution when using these products. Inhaling the oil vapors can cause an allergic reaction in some people, and citronella oil may also irritate sensitive skin. Citronella is not edible, unlike its close cousin Cymbopogon citratus, commonly known as lemongrass.

If you have bought a ‘citronella plant’ with lacy foliage and a citrus scent, then it is most likely you have lemon-scented geranium, sometimes called the citronella geranium, which is actually part of the geranium family.  The lacy leaves smell similar to this grass, but the leaves do not contain the insect repellent citronella oil and therefore are ineffective at keeping those pesky mosquitoes from biting. Unfortunately, members of the geranium family may be beautiful plants for your garden amongst other flowers, but their lacy leaves just don’t repel mosquitoes well!

Common Problems

Citronella is an easy plant to look after with few growing problems.  Here are a couple of things to look out for just in case. Knowing these will help you maintain a healthy plant.

Growing Problems

Citronella benefits from afternoon shade to protect the leaves from sun scorch during the hottest time of the day. The scorched leaves are unsightly, and the damage reduces its ability to photosynthesize, thus reducing the overall health.

Wet feet can also be a problem for citronella.  Although they prefer soil to be consistently moist, heavy wet soil will reduce the ability to take up nutrients from the soil and will cause it to deteriorate. It may even cause root rot and the death of the grass. Grow citronella grass in free-draining, loam-based soil to avoid this growing problem.

Pests

This citronella is not affected by pests.

Diseases

Commercially grown citronella can be subject to leaf blight.  This is particularly prevalent in sub-tropical climates where plants are grown densely to produce citronella oil. Lack of air circulation provides perfect conditions for blight to take hold and will result in a reduction in both the quantity and quality of oil extracted. 

Blight is less common in domestic gardens unless plants are allowed to become very congested. Signs of blight are dark spots or lesions on leaves from which necrosis begins to rot the leaves. Remove and destroy affected leaves immediately. Divide congested plants every few years and remove dead or dying foliage to improve air circulation.

Frequently Asked Questions