The mosquito plant is relatively new to the plant world, coming into being during the last decade. It is not a plant that developed naturally but was made from two different plants. Mosquito plants usually present themselves as a potted plant to be placed on the patio table and are reported to keep mosquitoes away because of their citronella--like scent.
The mosquito plant is an attractive plant with delicately serrated leaves that are somewhat fuzzy and green and tiny lavender flowers. The species name is Pelargonium, a scented geranium that has many different types with many different scents like apricot, strawberry and chocolate. The mosquito plant grows about 1 foot in height when in a pot but can grow higher in warm climates. It is very bushy and usually fills the pot with its leaves.
The plant was developed by Dutch botanist Dr. Dirk Van Leeni, who took chromosomes of Chinese citronella grass and combined them in an African geranium or pelargonium. The result was something that looked like a geranium but had that lemony citronella scent. Citronella is a substance used for many years that was made into candles or in aerosol sprays to keep mosquitoes at bay.
A mosquito plant must be purchased and can be placed in a 4-inch or larger pot. Several plants can be placed in a 12-inch or larger pot or in a flower box planted 8 to 10 inches apart. The plant is very bushy and will fill the space in nicely. Plant the mosquito plant with potting soil that is well-drained. Mosquito plants can also be propagated by cuttings. Take a long stem from the plant and remove all but the top leaves. Dip it in rooting hormone and then in a light planting medium that has been put into a flower pot or peat pot. Keep moist but not so moist that mold grows. Keep in a warm area for about one week then move to a sunny window or under a grow light. Plant in pots once several leaves have appeared.
Place pots in full sun. The mosquito plant will tolerate partial shade but will not grow to its full potential. This is a tropical plant and will continue to grow year-round in warm climates. It will not survive a frost in cold climates. The plant must be treated as an annual plant or taken in and grown under grow lights during the winter. Water the plant when the soil feels dry and make sure to pull off any leaves that have yellowed or dried. It generally does not need to be fertilized but if it is in the same pot for over a year it will benefit from a bit of houseplant food.
Effect on Mosquitoes
The scent of the mosquito plant confuses mosquitoes. Normally they can detect food with a special type of radar. When citronella is present they can no longer smell and therefore cannot find their prey to bite them and suck their blood. The scent blocks their radar and, until the scent is gone, they will not recognize that any food is nearby.
The University of Guelph in Ontario, Canada ,performed a study on the mosquito plant. Researchers captured and placed mosquitoes in a Plexiglas cage, then inserted volunteers' arms into the cage. There was not much difference in the number of bites the arms received with or without the plant in the cage. They also tried it with lemon thyme and mosquitoes did not bite as much as with the mosquito plant in the cage. They also tried the experiment after crushing leaves of the mosquito plant and rubbing them on the arms. It did reduce the number of bites somewhat. Many people who use mosquito plants would differ with this study. They say mosquitoes do not bite nearly as much if the plants are situated on a patio or porch. However, there needs to be many plants to affect an area that is not protected.