Man's best friend, but what about your trees?

The Dog: Not Always a Tree’s Best Friend

June 16, 2010
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There is a dog in our neighborhood. He is an old golden retriever who is never on a leash. When other dogs pass by, he lets out weak barks - more like huffs, actually.

Johnny Utah is his name. He's a sweet dog with a bit of a sad, wise face that usually wears a red bandana. In fact, he reminds me of a friend of his name sake - the character Keanu Reeves plays in 1991's hit "Point Break." Like Patrick Swayze's Bodhi, he's like an old surfer dog.

But unlike Bodhi and his gang, he is never suspected of mischief. Yet I know he causes death and destruction in front yards up and down the street. I have seen him commit countless murders … and I suspect his involvement in others even though I haven't been an eye witness. Mark my words: Soft, fluffy, golden-haired Johnny Utah is a killer.

Shrubs. That's right - Johnny Utah kills shrubs. He walks around the front yards around his house and conducts his business. My one neighbor had to replace her sedum   and its beautiful rose-colored blooms three times as a result of Johnny Utah's powerful weapon. He's killed other perennials too, and though I haven't seen him murder a tree I have seen him weaken one with his strong "perfume."

But because he's so weak and quite sad looking, none of us complain. But, make no mistake about it, his urine hurts trees and plants.

"The acid eats right through the bark and cambial zone to the wood zone, destroying the tree's defense system," says Eric Fleisher, the director of horticulture at the Battery City Parks Conservancy, which oversees the public park at the lower tip of Manhattan, adding that even a small opening in the bark is a gateway for micro-organisms that can spread disease through a tree.

In a story in The New York Times, Fleisher discussed the devastated base of a 15-foot linden tree near the walkway along the Hudson River. He pointed out that urine usually contains a lot of salt, which deprives the plant of water and can burn roots. The linden's bark was eaten away, exposing the living tissue where water and nutrients flow. The tree had tried to curb the damage by forming a knobby ridge of calluses. But it was no use. The tree's base was stained dark gray and the bark deeply fissured - from dog-leg-level down. The soil was hard from constant dog paw traffic, suffocating the roots.

Of the 24 trees Fleisher replaced in one year, six were due to dog urine - and trees at park entrances are usually the first to go. And when plants are weakened and stressed, they are also susceptible to insects and disease, he says.

To offset the acidity, Fleisher says Battery Park landscape professionals add lime to the soil. And to counteract ground compaction, lighten the soil and neutralize the salt, they add gypsum. Aeration can also open up the soil and help roots breathe, and mulching and adding organic matter to the soil also helps keep soil moist and provides plants with valuable nutrients.

Planting a tree at the proper depth can also help give it "a leg up, so to speak, on dogs," the article reported. Planting too deeply forces the roots to grow upward seeking oxygen. The bottom of a trunk flare should be flush with the ground, Fleisher points out. "The periderm is much tougher in this area so it won't deteriorate as fast from dog urine," he says, adding that bark higher up is less resistant.

Ultimately, the best thing anyone can do is train their dog to use the street, sidewalk or more resistant turf as a restroom, Fleisher encourages.

The good news: You can have the best of both worlds: a happy dog and a healthy tree.

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