This is a question that keeps cropping up, in some form or other, year after year. The reason for that is probably because the answer to the question is, “It depends.” If your wish is to have plants in your garden that will repel mosquitoes by their very presence, there are a few choices, but you will need to plant a whole lot of them, and they will not be 100% effective. On the other hand, if you seek to grow plants that will repel mosquitoes when their compounds are applied to the skin, there are several other possibilities. Basically, mosquitoes are repelled actively or passively. Passive repellants mask the scent of whatever attracts mosquitoes in the first place, thereby encouraging them to look elsewhere. Active repellants either have a scent that mosquitoes dislike, or contain at least one substance that is toxic to mosquitoes, thereby causing them to avoid the area.
Basil (Omicum, many varieties) – Several studies have been conducted on the effectiveness of basil in repelling mosquitoes. Unlike many plants, basil does not have to be touched or crushed in order to give off its strong scent. The hotter it gets, the more of the pungent essential oil is released from the plant. Of course, when the leaves are crushed, the scent gets even stronger, and the essential oil will stay on the skin. Such direct application is up to 100% effective in repelling mosquitoes, at least temporarily. Having a lot of basil growing in the garden, rubbing some its leaves over your skin while you’re out there, and burning more of the leaves while you’re grilling, would seem to be an effective three-pronged approach during the worst of mosquito season. Inside, some potted basil in each room, and more leaves in a potpourri warmer will likely send any stragglers packing.
Wild Sage (Lantana camara) – This tropical native has been so widely distributed as an ornamental plant that it has become invasive on some parts of the planet. Like basil, the most effective way to use it as a mosquito repellent is to grow a lot of it, apply it to the skin, and either heat it or burn it.
Thyme (Thymus, many varieties) – The main mosquito-repelling ingredient in thyme is an essential oil known as thymol. Direct application is up to 97% effective, while burning the leaves will provide about 90 minutes of 85% protection.