While many plants are referred to as "mosquito plants," they need to be crushed or have the oil extracted in order to repel mosquitoes. The Iowa State University Extension service explains that the best way to use these plants to repel insects would be to break up the leaves or stems and rub them on your skin. Before you do this, you should do a small patch test first to make sure your skin is not too sensitive to the oils.
Catnip is an herb that is best known as an ingredient in cat toys, as it is a stimulant for them. The oil secreted by the catnip plant contains compounds that include citronellal, citral, carvacrol, geraniol and pulegone. According to the College of Natural Resources at Virginia Tech, these compounds all act as insect repellents. Catnip has been found to be as effective as DEET in repelling insects. A study in the September 2005 issue of "Medical and Veterinary Entomology" reports that not only is catnip as effective as DEET, but DEET is a potentially toxic insect repellent, while catnip is safe, except for minor skin irritation in some people who come in contact with the oil.
Marigold is a plant that have some repelling ability while they sit in the pot. New Scientist magazine reports a study in which researchers at the University of Alabama found that, after checking all parts of the marigold plant for insecticidal properties, the flowers of the marigolds were the most potent part. You many need to have several pots on your porch or deck to repel mosquitoes.
Rosemary contains oil that holds many health benefits from the ability to treat vertigo and circulatory problems to anxiety and depression. The "Herbs 2000" herbal encyclopedia adds that it can also be added to bath water to promote relaxation for the body's muscles. Along with healing properties, it is used in many culinary dishes, and you can add mosquito repellent to the "uses" list. If you crush the leaves or rub them on the skin, rosemary oil can ward off the pests.
Lemon thyme is most often used as a culinary herb and is often found in backyard herb gardens or on a kitchen windowsill. When you crush lemon thyme leaves to use in your next recipe, crush a leaf or two to use as an insect repellent. According to Iowa State University, crushed lemon thyme contains 62 percent of the mosquito repellent properties that DEET contains.