Do Citronella Plants Repel Mosquitoes?
Yes and no. There are two different kinds of citronella plants and only one has any effect on pesky insects. But they're both nice to grow.
Do citronella plants really repel nasty mosquitoes?
The answer is both yes and no. Although citronellas are nicknamed mosquito plants, they don't always do the trick at keeping the pests at bay. There are two different kinds of citronellas — citronella grass and geranium citronella —and one, the grass, can be effective if the oil is correctly extracted.
Cymbopogon nardus is a tropical-looking, clumping grass native to Southeast Asia. Oil from this citronella grass is extracted commercially and used to make products like citronella candles, incense and sprays. Most researchers say they're effective, natural mosquito deterrents, at least to some extent.
Citronella grass by itself won't repel mosquitoes. You have to extract the oil, which you can do by simply crushing or rubbing the leaves against your skin. Be safe and try this on a small patch of skin at first to make sure you won't have an allergic reaction.
Citronella grass is hardy in Zones 10-12, and its coarse-textured leaves can grow to six feet tall and wide. It looks very similar to lemongrass and is often mistaken with it. Citronella grass thrives in bright, filtered sunlight and needs moist, loamy soil. Citronella grass is very thirsty, so you may need to water as often as once a day. To make more plants for your garden, divide the grass into clumps and replant them in the spring. Feed them with some nitrogen-rich fertilizer, following the directions on your product for how much to use and when to apply it.
The other kind of citronella, Pelargonium citrosum, belongs to the geranium family. Like citronella grass, it has a lemony or citrusy fragrance, but most researchers agree that it is not effective at keeping mosquitoes away. However, it's easy to grow for its nice scent, pretty blooms and lacy, medium-green foliage.
Citronellas related to geraniums need six to eight hours of sun a day and are winter hardy in Zones 9-11. They can be planted in the spring after the last frost has passed and the soil has warmed up, around the time you plant tomatoes. They like moderately rich, moist soil. Space them 18 to 24 inches apart in beds, borders or containers. It's nice to plant them where you can brush the leaves as you walk by, so you can enjoy the scent they release when they're bruised.
While citronella geraniums can tolerate some drought, they grow best when watered regularly. Poke your finger into the top inch of soil; you'll know it's time to water when the soil feels dry. They also appreciate regular feedings with all-purpose plant fertilizer. Follow the directions on your product to know how much to use and how often.
To overwinter citronella geraniums, pot up the plants in containers with drainage holes and fill them with good quality potting soil. Then bring them indoors and give them a spot in a sunny window or under a grow light. Move the plants back outside when the weather is reliably warm. For best results, help them reacclimate to the outdoor conditions by giving them a little more time in the sun and wind each day for one week up to 10 days.
How to Harvest Citronella Oil
To make your own natural mosquito repellant, combine 1 cup of olive oil with 1/4 cup of citronella grass stems and leaves in a slow cooker and cook them for four to eight hours. Then strain the mixture through a cheesecloth into a clean, dark jar or glass. To make the oil more fragrant, add fresh leaves and stems to the olive oil, but not more olive oil. Strain the mixture again and repeat the steps until the citronella oil is as fragrant as you want. Store the citronella oil in a dark, cool place for up to six months or add it to candles and lotions. Be safe, and never ingest citronella oil.