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Follow the nose: How to keep moles out of your yard

Friday - 8/1/2014, 4:50am  ET

Don't like the smell of castor oil? Neither do moles and voles. Use it to help keep these critters away. (Thinkstock)

A new way to deal with moles

Connor in Fairfax writes: "I'm having trouble with moles. They used to just be in my backyard, but now they're making their way to the front. I treated for grubs last summer/fall with milky spore powder. Would it be a good idea to treat my lawn with it again? What is the best way to get rid of moles?"

The milky spore was a good start, Connor. This naturally-occurring soil organism would have wiped out any grubs that were in the turf when you applied it. And it will continue to make that soil grub-unfriendly for decades, eliminating one of the moles' favorite foods. But it doesn't affect their other underground food sources, like earthworms and sleeping cicadas.

The next logical step would be to treat the soil with a high concentration of castor oil, preferably a professionally-packaged product, like "Mole Med" from Gardens Alive. The castor oil infuses the soil with a scent that makes moles (and voles) miserable and hopefully drives them away. After that, we're talking spring-loaded traps, which are large, cumbersome, and can be difficult to set.

But now there's another option, new just this year: an FDA and organically approved (OMRI listed) treatment called "Mole Zap." It uses CO2 cartridges to eliminate the bothersome burrowers by displacing the oxygen in their runs. The company behind the product just sent me some samples, and the device looks pretty cool and easy to use — but I have no moles to test it out.

So I'm very interested to hear from listeners with mole problems who try this interesting new alternative. Here's the link to the product on Amazon, where the reviews are mostly very favorable.

(Note: The device is approved for use in Virginia and Maryland, but seems to be restricted in the District.)

Yellowjackets are building their armies

Jonathan in Largo writes: "Thanks for the information a few weeks ago on yellow jacket nests in the ground. I have a hole in my lawn with many ‘bees' going in and out and now I know that they are not bees. You said to place a large glass bowl over the hole on a cool morning to trap them underground. Does this mean that I have to wait until the fall? Or would a cool early morning in the summer work just as well? In the meantime, I have to cut my lawn; how close can I get to the opening without aggravating them?"

No! If you go anywhere near an underground yellowjacket nest with a noisy mower or weed whacker you will be stung many times, perhaps unto death, Jonathan!

And yes, I meant on a cool evening now. That nest is getting bigger every day, and we've had the kind of almost-record-breaking cool nights that make this simple trap placement safe and easy! Put that bowl in place on the next cool evening before you discover how super-aggressive these dangerous members of the hornet family can be.

Where, oh where have my hydrangeas gone

Pat in Calvert County writes: "I have had ten hydrangeas in my yard for many years, and every year they've produced beautiful bouquets for me to bring to work. This is the first year that not one of the bushes has bloomed, regardless of location. Could it be because of the cold winter we had? Also, I sometimes cut the plants back in the fall; is that when you're supposed to cut them back?" 

No, Pat. No perennial plant should ever be cut back in the fall — never, ever. It interferes with their ability to go dormant for the winter and could cause permanent harm. And fall pruning can accidentally remove lots of the flowers-to-be from blooming plants.

The best way to prune hydrangeas is to leave them alone until all the flowers have formed in the late spring/early summer. Then remove all the barren branches hiding the flowers. (It's a great trick that makes the plants look really full.)

And your lack of flowers is the rule this year, not the exception. Few to no hydrangeas are blooming in our region thanks to the crippling once-in-every-20-year winter we barely survived.

Enjoy all the lush greenery that reveals that at least the root systems survived. And don't prune them until the flowers form - hopefully - next summer.

Hands off that myrtle until spring

Sue in Waldorf writes: "When is the best time of year to prune crape myrtles? And how much should be taken off?"

The only good time to prune a crepe myrtle is right after it begins growing again in the spring, Sue. Pruning it now or in the fall could cause severe winter damage.

And the ideal is to take off about as much as it grew the previous year to keep the blooms approximately at eye level. Don't commit "crepe murder" by hacking it all the way back to the ground. These plants may survive such attacks, but you eventually end up with lopsided tiny branches growing out of massive trunks.

Lilacs are lovely from laurel to linganore

Sue in Waldorf also writes: "And I'm thinking of planting a lilac; when is the best time of year to plant? And do lilacs thrive in Maryland?"

Yes, they do — if they have full sun, good airflow and excellent drainage. You can plant lilacs in the spring (the most traditional time) or in the fall (an excellent time if you can find nice specimens for sale). But don't plant any kind of perennials in the summer.

Suddenly not shady

Tim in Frederick writes: "My landscape has suffered the loss of several trees over the past six months, and my yard has gone from shade to full sun in one fell swoop. I think it may be necessary to move the hostas and ferns to a shadier part of my yard. Should I move them now or wait until fall? I'm worried that these shade-loving plants might be damaged by the sun they'll be receiving from noon until sunset the rest of the summer."

They won't be damaged, Tim. Most of our hostas have already flowered and set seed, and that means that their leaves have begun "turning off" for the year. And this season has been unusually cool and wet, which allows shade-loving plants to tolerate more sun.

You can move them in the fall, but I suggest waiting until next spring when the hostas and ferns break ground for the season. That's when they're the strongest and can best take transplanting and dividing if they've gotten big and crowded, the way hostas tend to.

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