While there are many plants that can repel mosquitoes, most of them work by producing oils, like citronella, that the insects dislike. These plants work best when the leaves are crushed and the oils they excrete are rubbed onto the skin, and as such Iowa State University expresses skepticism as to whether simply planting them near patios and other outdoors spaces provides adequate mosquito protection. It certainly doesn't hurt to try these plantings, however, and if you do, you'll have their leaves handy on occasions where extra skin protection is desired. There are both herbs and flowers that may help keep mosquitoes away.
Commonly found in bug-repellent candles and sprays, citronella is a lemon-scented chemical produced by certain plants. To ward off mosquitoes, you must be sure to use the true citronella plants, like lemongrass (Cybopogon nardus) or Java citronella (Cymbopogon winterianus), as other varieties of plants marketed as containing citronella don't repel mosquitoes as well. Lemongrass is found in U.S. Department of Agriculture plant hardiness zones 10 through 12 while Java citronella will tolerate the slightly cooler climate of USDA hardiness zones 9 through 11. Both plants can be grown as annuals in cooler climates.
Also known as horsemint, bee balm (Monarda spp., USDA zones 3 through 9), is an herb that flowers in shades of red, pink, purple and white. Bee balm attracts butterflies and birds while repelling mosquitoes and resisting deer. It also resists drought and is simple to grow, making it an excellent choice for new gardeners.
If you hate flies as much as you hate mosquitoes, try repelling both with plantings of annual basil (Ocimum basilicum). Basil has a pleasant smell in the garden, adds zest and flavor to spaghetti sauce and will keep both flies and mosquitoes at bay. A sunny spot and well-drained soil are all you need to make basil thrive.
Though planting it may not be the best plan if you're trying to keep stray cats out of your garden, Earth Easy reports that a 2010 study found catnip (Nepeta spp., USDA zones 3 to 4) to have more mosquito repellent properties than the chemical DEET commonly used in insect repellents. Catnip will grow as a weed, so it is extremely simple to grow in containers or cultivated garden beds.
Grown as annuals, floss flowers (Ageratum spp.) are low plants that work well in rock gardens and other spaces where tall plantings are undesirable. Floss flowers produce small, round, soft flower clusters in blue, pink and white hues throughout the summer and fall. They also produce a chemical called coumarin, which is offensive to mosquitoes. Fertile soil is required, so you may need to fertilize floss flowers, but these attractive mosquito-repelling plants are worth the effort.
Marigolds and Chrysanthemums
Both marigolds (Tagetes spp.) and chrysanthemums (Dendranthema grandiflorum) contain a chemical known as Pyrethrum, which is often used in insecticides and insect repellents. These plants are so repellent to insects and animals that even rabbits steer clear of them. Marigolds are grown as annuals while chrysanthemums are perennials in USDA hardiness zones 5 through 9. Both plants require full sun but are considered to be low-maintenance.
Lantana (Lantana camara) is a colorful annual plant that blooms in shades of pink, purple, white, red and orange from mid to late summer. Lantana repels mosquitoes but requires full sun and proper drainage in return. You'll need to prune this bushy plant often to help it stay more compact and keep it from getting leggy, but the plant is not invasive and grows well in containers. Be sure to take a whiff of blooming lantana before purchasing it for your garden; the flowers produce a strong odor that not everyone enjoys.