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Gardening Q & A: Evergreens, Outdoor Light and more

Here are tips on snow-covered evergreens, harmful effects of outdoor lights, banned cypress mulch and using caffeine to deter snails and slugs.

Master gardener Paul James answers questions about evergreens, outdoor lights, cypress mulch and slug deterrents.

Q: Help! My evergreens are hugging the ground after weeks of being covered with heavy snow and ice. How do I help them straighten up?

A: That's a situation that I have to deal with just about every year. The Leyland cypresses behind me should be at least two to three feet taller than they are at the moment, but a heavy snow just a month ago caused them to hug the ground. The only real solution is to stake and tie the trees to give them the support they need to grow upright again.

To keep my trees standing vertically, I drive steel rebar stakes into the ground nearly three feet deep. I use strong jute or nylon string to make a loop around the tree and tie to the stake. I like using rebar for projects like this because it's flexible and it bends well in the wind. You can use wood sticks, but they need to be at least one inch square and ideally made of a rot-resistant variety like redwood or cedar. No matter which you decide to use, chances are that you'll be able to remove the stake after three months because by that time, the sap will begin to flow into the branches. The trees should be able to support themselves — at least until next winter.

Q: Can outdoor lights have harmful effects on plants?

A: Most outdoor lights used in the landscape don't pose a threat to plants. Whether low-voltage lights commonly sold in kits, incandescent lights used mainly on patios, or mercury vapor and metal halide lights — the reason is simple: the light they emit isn't intense enough to hurt plants.

However, during the mid-60s, homeowners' concerns about neighborhood safety led to the introduction of high-pressure sodium lights. Today, these lights can be found in virtually every city in the country, including my own yard. Short of actually contacting your local utility to find out what kind of light you have, you can be reasonably sure that if the light emitted is a golden yellow rather than white, you have a high-pressure sodium light. And high-pressure sodium lights can indeed affect the growth of plants.

Telltale signs of plants suffering from high-pressure sodium lighting include delayed dormancy, which is characterized by leaf retention beyond the normal period of growth; or shoots that continue to grow rather than go dormant, especially those nearest the light; or spring die-back that results from delayed dormancy the previous fall. If you suspect the lights in or near your landscape are causing problems, then contact your local utility and ask to have deflectors installed to direct the light away from your plants. Or consider switching from high-pressure sodium lights to some other form of light.

Q: I live in Florida, and my city recently banned the use of cypress mulch. Any idea why?

A: Cypress mulch has been banned in several municipalities, particularly in Florida, because of environmental concerns. Nearly 130,000 tons of cypress mulch is harvested every year from Florida's wetlands. And some experts believe that these slow-growing trees, which are a critical component of the wetlands ecosystem, are disappearing at an alarming rate. Thankfully, there's a great alternative to cypress mulch for southern gardeners. It's melaleuca mulch, which comes from the melaleuca tree.

Q: I heard that caffeine deters slugs and snails. Is that true?

A: Caffeine not only deters but can destroy both slugs and snails. In fact, in tests conducted by the USDA in Hawaii, a 2 percent solution of caffeine was found to be more effective than the highly toxic metaldehyde, the active ingredient found in most commercial slug and snail baits. In fact, a solution containing only 0.1 percent caffeine, which is roughly the equivalent found in one cup of regularly brewed coffee, was found to be effective against all but the biggest slugs. Of course, further research is needed, but given the promising results thus far, I wouldn't be surprised if products for controlling slugs and snails containing caffeine wind up on store shelves in the next few years. In the meantime, however, I'll continue to rely on all-natural products like those containing iron-phosphate or traps that make use of another popular beverage, beer.

— Paul James, master gardener and host of Gardening by the Yard

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