Plants you can grow to keep away menacing mosquitoes

The Zika virus has taken mosquitos from outdoor annoyance to fearsome foe. Mike McGrath, host of You Bet Your Garden, will review the plants you can grow to use as mosquito repellant. Plus answers to all your growing questions.

Questions of the Week:

“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

Repel mosquitoes naturally »

Highlights from show for July 9, 2016:

Splitting tomatoes

John from Houston, Texas is curious about splitting tomatoes and whether they continue to absorb nutrition even after they start to ripen. He has heard that once a tomato starts to ripen, it’s actually separated from the mother plant. Is this true? “The problems with tomatoes splitting become the most evident when the tomato is very close to ripe, or dead ripe,” Mike says. In other words, the plant must still be accepting water from the root system or else the skin wouldn’t split, so it is indeed still absorbing nutrition. “Don’t be afraid to harvest a little bit early,” Mike also advises. You don’t only taste a tomato with your taste buds, but with your nose, due to volatile, aromatic oils that build up as the tomato is ripening. If a tomato becomes dead ripe and sits on a vine, it can lose up to 30% of its flavor in one day, because those oils are so aromatic. John should harvest around what tomato professionals call the “breaker” stage- when the fruit has received about half its color. The tomato will then continue to ripen fully off the vine. John recommends the website Tomatoville to fellow listeners for additional tips.

Composting cedar apple rust

Lisa from Smithfield, Virginia- the ham capitol of the world- wonders if she can remove and compost cedar trees that have been infested with cedar apple rust spores. She is fearful of infecting additional trees. “Cedar apple rust is one of the weirdest diseases in the plant world,” Mike says. “It needs both hosts- a member of the cedar family and a member of the apple family.” The disease is then passed back and forth from both hosts, and results in an orange growth Mike likens to little Chinese lanterns. Mike suggests Lisa get rid of the apple tree and monitor the cedars over the next two years or so. Without the disease’s other host, the cedars should improve.

Rabbiteye blueberries

Ron from Rincon, Georgia is growing rabbiteye blueberries and plans to extend the plot across his entire acre into a makeshift blueberry farm. “That can bite you- to have a monoculture like that,” Mike warns. He advises Ron to break up the stretches of blueberries with something different in case a pest or disease finds his farm and takes advantage of the continuous fruit. As for Ron’s current plants, Mike says not to prune until winter’s end and to keep the orchard floor clean of weeds and dead fruit. “Weeds and birds are the worst banes of blueberry growers,” Mike says. “You want to have lanes that are wide enough to mow. Then it’s hand cultivation with specialized hoes and gentle weed whacking.” Mike advises Ron to have a gardening partner use a piece of PVC pipe against the plant for protection while he tackles the weeds. In addition, Ron should go out and get milled peat moss, putting it down as a mulch and covering it with compost, which would both feed the plants and keep the soil acidic.

Combatting squirrels

Ken from Media, Pennsylvania has squirrels eating the fruit from his peach, nectarine and cherry trees. He asks Mike what he can do to protect the fruit and keep the animals away. Mike explains that Ken has a case of what should be referred to as “evil” squirrels, who are getting at the trees from the ground up. Since the trees are too far apart for the squirrels to leap from the branches of one to another, Mike suggests that Ken use a sticky substance called Tanglefoot. By painting this on the middle of trunk, Ken would protect the fruit from the mangy animals, who would shy away from getting tangled in the glue-like barrier. Ken could also aim motion activated sprinklers at the trees. “The nice thing about the motion activated sprinklers is that you can move them around and aim them at different plants, wherever you are getting attacked,” Mike says. He also advises Ken to use Surround, a micronized clay spray, several times a season to protect the trees from insects and disease.

Proper tree planting

Colin from Kingston, Ontario planted a sugar bush maple tree that died quickly after bloom. He asks Mike what caused the young tree to turn so brown and dry. Unfortunately, Colin made a few simple, but damaging mistakes. By placing the tree too deep, Mike says he “planted it like lollipop,” suppressing the roots from flaring above ground. Colin had also used a wood mulch, which can inhibit proper breathing and allow for insects and mice to attack undetected. Above all, the young maple lacked a correct watering schedule. Colin watered the tree upon planting, and again in weekly intervals, which is not enough for a brand new bloom. “I think it probably died from lack of attention,” Mike tells Colin. “What you should have done is drag a hose over and let it drip at the base for about 24 hours…then if it doesn’t rain in the next couple of days, you do that again.” For the first year, a newly planted tree should get a good soaking a few times a week. “The biggest cause of premature tree death is inadequate watering in the first week,” Mike says. He recommends that Colin see if the tree is salvageable by digging it up and checking for rotten bark underground. If it is indeed dead, Colin can look for a replacement to plant again in September after the hot summer has passed.

How to fertilize your plants

Paula from Newtown Square, PA is having problems with her rosemary plants, whose leaves are becoming stippled by tiny gray insects. She has them situated outdoors in ceramic pots and is feeding them with Miracle Grow and horse manure. Mike immediately notes that this mixture is harmful. Miracle Grow makes the soil too salty, an effect similar to growing too close to the ocean, and horse manure does nothing beneficial. “Rosemary bushes are Mediterranean plants that thrive on poor soil, good drainage and little to no extra nutrition… I would rather you feed them nothing,” Mike says. “These are what I consider- in a good way- ‘trash plants.’ They get by great with no nutrition.” As for the bugs, Mike tells Paula that for the next five mornings she should cradle the plant in one hand and use the other to spray a laser sharp beam of water at the insects, blasting them out of the plant. “Be relentless,” Mike says. Do each plant in a row, again and again, early in the morning, continuing for two days after the bugs are gone. According to Mike, “water is the best pesticide.”

Rose chafer beetles

Ken from Roscommon, Michigan has a backyard filled with wildlife but infested with rose chafer beetles. Rose chafer beetles are from the Scarab family, which leave behind a lacy destruction on leaves. Mike recommends that he combat the insect eggs with beneficial nematodes- tiny microscopic wormlike creatures- which he can water into the ground. When ready, Ken should soak his garden, drop the nematode sponge into a watering can to release 50 million of these microscopic predators, and then water around the areas underneath where he had the worst infestations. Overnight these nematodes will bury into the soil and attack the eggs and larva of the chafer beetles. “You also definitely want to apply milky spore in the fall,” Mike says. This is a naturally occurring soil organism that inhibits the development of Scarab pests. “At the end of the summer, apply this milky spore powder to your entire landscape,” Mike tells Ken. “It will go down into the warm soil where the beetle grubs will ingest the spore…they die and their body turns into a milky spore factory…that way you knock out next year’s generation in advance.”