WASHINGTON – John and Marsha, who have “a ground-floor condo with an outdoor patio in the tropical swamp of downtown D.C.,” write: “We have a big mosquito problem in the summer and we’re interested in a sustainable way to be able to use our outdoor space. We’ve heard that having a few pots of citronella grass (Cymbopogon nardus) on the patio might help. But where can we buy it? And WILL it help?”
The basic answers are no and no. Citronella is a tall and unattractive tropical grass that is not generally available for sale in the United States, would not do well in the D.C. region, would not survive in a pot and is invasive in its native Africa. The mosquito-repelling oil it produces is harvested from the roots, so citronella is a natural product, but an imported one.
Plants that are just growing in pots have no power to repel mosquitoes. There are plants you can grow in pots that will repel mosquitoes if you crush up the leaves and rub them on the exposed areas of your skin. But a big outdoor fan might serve you better. Mosquitoes are weak fliers and the breeze will feel great.
These plants repel mosquitoes when crushed and rubbed
John and Marsha in the “tropical swamp of downtown D.C.” have a big mosquito problem in the summer and want to know if potted plants can help keep them bite-free. In the pot, no. But crushed up and rubbed on skin, yes.
In controlled medical studies, the crushed leaves of lemon-scented thyme repelled mosquitoes as well as some concentrations of the dangerous chemical repellent DEET. The only downside is that thyme is a small, rock-garden kind of plant that won’t produce enough leaves over the course of a summer to do much good.
That’s why I rely on lemon balm. This aggressive member of the mint family is much easier to grow in bulk and almost as effective. A couple of pots of lemon balm will provide plenty of big, wonderfully-scented leaves to crush. Just be careful to keep it under control, though. If you plant it in the ground as opposed to in a pot, it will take over.
Lemon-scented geranium is also effective. It is the famous “mosquito-repelling plant” you see in magazine ads. In fact, all lemon-scented herbs have mosquito-repelling power when crushed and spread on areas of exposed skin.
Catnip has even more repelling potential than lemon-scented herbs. But if you grow that one in pots, you’ll have every stray cat in D.C. sharing your backyard.
Other ways to deter mosquitoes: Fans and traps
I want to return to my first suggestion of having a big outdoor fan blowing behind you when you sit outside in the evening. It’s an underutilized but highly effective way of not giving blood a hundredth of a dram at a time.
Mosquitoes are very poor fliers. They can’t battle against a breeze and the air will make you feel good. Mosquitoes also only breed in still water and females don’t travel far from where they hatch, so make sure there is no standing water outside. Check your gutters, too. They can be a big unseen breeding site.
Or, go the other route and set out water traps. Get a jug of all-natural BTI granules and shake some into water containers outside. Female mosquitoes will lay their eggs in the water, but the BTI will prevent them from becoming adults without creating any danger to you, your children or your pets. Your dog can even drink the water safely. BTI granules are available for retail sale under the Summit brand name and can be mail-ordered from Gardens Alive.
Now those evil squirrels are deflowering roses
Elaine in Locust Grove writes: “How do we stop the squirrels from eating our rose buds and blooms? They have been caught in the act!”
Evil squirrels are the nemesis and bane of all good and decent gardeners, but you have the upper hand here, as they’re eating ornamental plants rather than garden edibles. I suggest you spray the buds heavily with either a super-strong deer repellent whose active ingredient is putrescent egg solids or a “hot pepper wax” spray. When they get a taste of either of those, they will find their evil joy elsewhere.
To try and minimize squirrel problems, don’t put out birdseed in the summer. The birds do not need it and it attracts squirrels like a magnet. If a neighbor is actually feeding the terrible tree rats directly, beg them to stop (or spray the squirrel food when they’re not looking).
Mowing a dry lawn is good for the grass and for toads
Susan in Kensington writes: “I’ve read that it’s best to mow the lawn in the evening. Is this correct?”
Catherine in Woodbridge writes: “I have lots of small toads in my back yard and don’t want to hurt them when I mow – I know they eat lots of bad bugs. I’ve got my mower set to a high level, but they still jump into the blades. Can you suggest how to mow safely? Is there a better time, like midday?”
These questions couldn’t be more different, but the answer is actually the same.
The best time to mow for the health of your lawn is when the grass is bone-dry, toward the end of a sunny day. Lawns are generally wet with dew in the morning and cutting wet grass rips the grass blades apart, rather than slicing them cleanly.
Toads are mostly nocturnal and are always creatures of dampness. They shun sunlight and dryness, so right at the end of a bright and sunny day is the best time to mow without hurting them. But even one hurt toad is too many, so go over the area with a leaf blower set on high before you mow to frighten them away without any risk of injuring them.