Citronella is a great plant for the garden, containers, window boxes and it even makes a good houseplant. It has lots of pink blooms and interesting lacy leaves. Its best feature is the lemony scent that fills the night air. It is easy to grow from seed or cuttings and can be overwintered from year to year. Here’s everything you need to know about growing citronella plants.
Quick Guide to Growing Citronella
- Plant in spring after the last frost date.
- Give each plant 18″ (45 cm) of space and plant in well draining soil.
- Water well and then don’t water again until the soil needs it.
- Fertilize if planted in a container, window box or low nutrient soil.
- Treat like your other annuals, but remember to bring it in for the winter.
This plant is sold under a variety of names which makes it a bit confusing. The most common citronella plant is a type of so-called ‘scented geranium’ except that garden geraniums are not actually geraniums – they’re pelargoniums.
In North America the plant goes by several names including Pelargonium (aka geranium) citrosum, mosquito plant, Pelargonium citrosum ‘van Leenii’, citranium or citrosa geranium. It is also sold as “Mozzie Buster” (Amazon link). The species P. citrosum does not exist and it is probably a cultivar of Pelargonium graveolens, so it should be labeled as Pelargonium ‘citrosum’. To learn more about plant name conventions see How To Name Plants Correctly – Botanical Names vs Common Names.
Whatever name you use, citronella is a great plant everyone should grow.
Does the Citronella Plant Repel Mosquitoes?
In short, no. Neither does the citronella grass (see below). The amount of oil given off by a living plant is far too small to repel insects. The same is true for citronella candles which also contain tiny amounts of the oil. Torches and bracelets with the same ingredient don’t work either.
Does the extracted oil repel mosquitoes? From a previous blog post, “Research in North America has confirmed that citronella oil is effective and the oil is registered as an insect repellant in the US. Studies in the EU failed to validate its effectiveness and they have banned the product as an insecticide. We must conclude from this that “we don’t know if it works”, but if Europe can’t find any evidence that citronella oil works, I tend to be skeptical.”
The insect repelling compound in these products is called citronellal. Oil from the citronella geranium contains 0.09% citronellal, while the oil from the citronella grass contains 14% citronellal. This clearly shows why the oil from the mosquito plant does not repel mosquitos.
Citronella Plant Care
Although the plant can be grown as a houseplant (see below) it is happiest growing in the garden. It will survive outdoors year-round in USDA hardiness zones 9b through 11 and in colder zones it can be treated as an annual or be overwintered indoors.
These plants like full sun but appreciate some afternoon shade in hot climates.
The plant is not fussy about soil but it does prefer well drained soil. Don’t amend the planting hole as you transplant. If you want to amend soil it is better to amend the whole flower bed at once, not an individual planting hole.
Citrosum is drought tolerant once established, but don’t let it get too dry. Water the same as all your other annuals and never water on a schedule. Use your finger and touch the soil to tell you when you need to water.
Plants in the garden rarely need to be fertilized and the mosquito plant is no different. If you must fertilize, use a water soluble fertilizer with an NPK ratio of 3-1-2. Or better still, just mulch with 2″ (5 cm) of compost. Avoid bloom booster products with a high phosphorus level because they don’t work.
Find out why a balanced fertilizer is always wrong: 10 Fertilizer Myths That Will Save You Money
This plant does not really need to be pruned, but as it grows, lower leaves may turn yellow as they age. The plant looks better if you remove these leaves. The plant will become bushier if you pinch the tips out. You can also harvest leaves at any time to add to small flower bouquets (tussie-mussies).
Growing From Seed and Transplanting
New plants can be easily started from seed but it may be easier to buy a small plant and make cuttings. Several sites suggest that you can direct sow, but the seedlings grow too slowly for this to work well. Instead start seeds indoors.
The best way to start seed is to use my baggy method as explained in this video. I’ve used the method to germinate several thousand different species of plants. Keep the seeds at room temperature and they should germinate in 1-2 weeks. Once germinated, give them more light for 12 hours a day and remove the cover so they are exposed to normal humidity levels. Treat like any other seedling. Start fertilizing with 1/2 strength, using an NPK ratio of 3-1-2.
Once the danger of frost is gone, plant outside with a spacing of 18″ (45 cm).
Propagate From Cuttings
Starting plants from cuttings is even easier than from seed and it’s a faster process. Using a knife or pruners cut a piece of healthy stem that is about 3 inches (7 cm) long. Ensure that it has 2 to 4 nodes – those are the bumps where leaves and stems normally grow. Remove all the leaves except for a couple at the top of the cutting.
Dip the cutting in rooting hormone if you have it, but it is not necessary because these cuttings root easily. In a simple experiment done at McGill University, 4 nodes produced more roots than 2 or 1 node, and rooting hormone produced the largest amount of roots.
Stick the cutting into some lose potting soil or pure perlite so the stem is mostly buried. Water and cover the pot with a clear jar or plastic bag creating a mini-greenhouse. This will keep the humidity high around the leaf. Provide bright light, but not direct sunlight. Wait. The cutting should root in 2-3 weeks. Give it a tug and if you feel resistance, it has roots. Remove the cover to reduce the humidity level and keep it watered.
There are three options for dealing with freezing temperatures. You can treat it like any other annual and do nothing, letting it die over winter. The second option is to bring it indoors and treat it like a houseplant until spring when it can be returned to the garden. The third option is to bring the plant in and store it a cool, dry place. Then in early spring, revive it indoors so it starts to grow and then place it outside. If your summers are longer, you can even revive it outside in spring.
Overwinter as a Potted Plant
Dig up each plant and remove most of the soil. Cut it back to about 6 inches (15 cm), plant it in a pot using a good quality potting media and place it in a sunny spot or under lights. Treat it as described below for houseplants.
The goal is to keep it alive and growing slowly over winter. If it grows too much, feel free to prune it back. As spring approaches, let it grow bigger so it is a good sized plant by the time outdoor temperatures are above freezing. It can then be taken outside and planted. Make sure you harden them off before you give them full sunlight.
Many people will do a hard prune in late winter and root the cuttings. By spring you will have several plants to add to your garden.
Overwinter as a Bare-Root Plant
Dig up each plant and remove most of the soil. Cut back to about 10 inches (25 cm). Place them in a cardboard box and store it in a dark, dry, cool (45 to 50 F, 7 to 10 C) location where it won’t freeze. The leaves will die back but the stems should remain green. It is Ok if they shrivel a bit. Check on them once a month to make sure they are not getting too dry. If they are, spritz them with a bit of water, but don’t make them too wet or mold will grow.
Revive them a month or two before your last frost date by bringing them into a warmer location and trimming off any dried leaves and stems. The main stems should still be green and a bit fleshy. Pot them up, give them light and water, and they should start to grow. They can be planted outside after the last frost date.
Mosquito Plant in Containers
This plant is a great addition to outdoor containers and window boxes. Treat like any other annual and keep it well watered. The potting media used in containers has no natural nutrients so it is important to fertilize regularly with an NPK ratio of 3-1-2.
Watering outdoor containers can be a real challenge in a warm summer. Watch this video to see how I plant containers so that they need much less watering.
Citrosum as a Houseplant
Citronella can be grown as an indoor plant but it may not be your best option. To do really well they prefer a temperature that is lower than most homes, 60 to 65 degrees F (15 to 18 C). They also like a lot of light so many home grown plants end up being tall and lanky. If that happens just cut them back to 6 inches and let them grow again. They also like humidity levels over 40%.
Grow them in a good quality potting soil, water as needed and fertilize at least once a month. Soluble fertilizer is the best option for houseplants since it can be easily added to the water used for watering the plant. Use an NPK ratio of 3-1-2.
Toxicity to Cats and Dogs
The ASPCA and the Pet Poison Helpline considers all geraniums to be mildly toxic to cats and dogs, if the plant is swallowed. “Geraniums contain essential oils (linalool, gerinaol) which can cause gastrointestinal upset or skin irritation with exposure. Symptoms can include vomiting, diarrhea, depression, lethargy, anorexia (i.e. lack of appetite) and dermatitis. Symptoms are usually mild and temporary”.
Geraniums are easy to care for and rarely have problems but the following may be issues.
- Brown Leaves indicate the plant is not getting enough water or too much sun. Water more often and/or move the plant to a shadier spot.
- Spots on the leaves can be a sign of bacterial leaf spot (also called blight). Symptoms also include leaf drop and black rot on stems.
- Water-soaked patches that turn corky is a disorder called oedema. It is usually caused by overwatering.
- Yellow leaves at the top of the plant can be an indication of root rot due to overwatering. If the roots are gone, take cuttings and root again.
- Thin, leggy growth indicates it is not getting enough light. Pinch it back and give it more light.
- Aphids, caterpillars, mites and whiteflies can infest geraniums but they are usually not a problem in a healthy garden with lots of predators. A strong spray of water can eliminate most problems, or use insecticidal soap until the pests are gone.
Citronella Plant vs Citronella Grass
People know this plant because they are familiar with citronella oil, but citronella oil is not extracted from the citronella plant. Instead the oil is extracted from various species of lemongrass (genus Cymbopogon), which are commonly called citronella grass and mosquito grass. The geranium contains very little citronella oil compared to the grass which is reported to contain 10 times as much. Lemongrass is a perennial clumping grass that grows to a height of 6 feet and is not frost hardy.
Frequently Asked Questions
Does the citronella plant really repel mosquitos?
It is sold as a ‘mosquito repelling plant’, but that is just marking misinformation. It does not repel mosquitoes.
Is the citronella plant a perennial?
It is a perennial, but only in warm climates (USDA hardiness zones 9b and above).
Is citronella plant safe to touch?
Most people will have no trouble touching the plant, but the sap can cause skin irritation in some people.
Are there culinary uses for mosquito plant?
Yes, you can use it for its citrus scent in jellies, teas, fruit salads, and desserts. Place leaves in the cake pan before adding batter to add flavor to a cake.