Using Plants and More to Repel Mosquitoes

Q. Mike mentioned a number of plants that can repel mosquitos on his Public Radio show several months ago; but my memory has failed me. Could you please go over the names again? Several of us down here are waiting to hear from you; we're on the water and have lots of mosquitos. We completely enjoy and learn from You Bet Your Garden!

--- Bettye in Oriental, North Carolina

A. Oh yeah—I'll bet they have a bumper crop of skeeters! We often vacation at a great little beach community just a little North of there—at the very Southern tip of the Virginia shore; and some years the number of mosquitoes hanging out up in the eaves of the house seems impossibly huge. But we always have a good supply of one of the plants she's asking about with us; trash bags full of lemon balm that I harvest from the garden right before we go down.

But we have to be really clear here—none of the plants we're going to name can keep mosquitoes away growing IN the garden or in a container; they contain great natural mosquito repellants that you have to apply personally.

Mosquito-repelling plants only work if you strip off the leaves, crush them up and rub them on your exposed skin. But they work very well when you do crush and rub them; the best ones are just as effective as the chemical repellant DEET or the top store-bought repellants whose active ingredients are based on plants. And home-grown plants are right at hand when the sun goes down and you're working in the garden.

I rely mostly on lemon balm because it's {cough; ahem} "easy to grow"—which is a synonym for invasive. I've been able to keep mine under control in actual raised beds, but less experienced gardeners will want to grow it in big containers because it can quickly take over. It's the same as mint; real easy to grow a lot of it whether you intended to or not. I'm willing to do the work to contain mine because it grows lots of big leaves really quickly, and every member of my family has had great success using it.

But in scientific studies, the absolute best lemon-scented garden plant for this purpose is lemon thyme. It's been shown to be highly effective when the crushed leaves are rubbed on your skin. But it's a smallish plant with fairly tiny leaves; you'd have to grow a lot of plants to be able to harvest enough to use on a regular basis.

And there's no downside there; it's a very attractive plant with a 'trailing habit' that makes it perfect for hanging baskets or growing over the top of large containers, like half whiskey barrels. And catnip may be even better; it's scored very high in studies using actual biting mosquitoes. Just don't blame me if you wind up with a garden full of intoxicated cats…

Two warnings: Even though there don't seem to be many reports of reactions to these plants (we actually couldn't find any), you should always test a little bit of any plant on, say—a part of one forearm—before you rub it all over yourself. And although some of the most effective plants are scented, don't try to use actual lemons or limes, as they are known to cause serious skin reactions.

Now let's review some of the other things you can do to ease mosquito problems; like having a strong fan blowing on you sideways when you're sitting outside; mosquitoes are poor fliers and can't fight a good breeze.

Empty standing water on your property; make sure your gutters are free of debris; and place BTI dunks or granules in containers of water you've deliberately placed around your home. Female mosquitoes will use the water as a breeding site, but the BTI—an all-natural soil organism—will prevent the eggs from turning into adult mosquitoes. And for the 18th time, BTI really is safe for frogs, toads, birds, bees, people and pets; it only affects mosquitoes, blackflies and gnats.

You should also enlist natural enemies to prey on the blood-sucking pests. Birds like swallows and martins eat enormous numbers of mosquitoes, so provide fresh water sources for them in the summer and nesting boxes or birdhouses geared to their specific species.

And don't forget dragonflies! These 'mosquito hawks' might be the best predators of adult mosquitoes—and you always see lots of them near the water. (Because as Willie Sutton famously said, "That's where the money is".) Here's a LINK to a previous Question of the Week on how to attract and keep these great mosquito eaters around.

And finally, store-bought repellants. There are several whose active ingredients have been shown to be just as effective as some concentrations of the chemical repellant DEET: Oil of lemon eucalyptus, which is distilled from the leaves of a species of eucalyptus tree native to Australia; picaridin, a synthetic version of a substance found naturally in the black pepper plant; and lemon scented geranium, which is the active ingredient in the repellants Bite Blocker and Sting Free.