Choosing Pet-Tolerant Plants

By Scott Aker
Special to The Washington Post
Thursday, September 13, 2007

Q I am looking for plant suggestions for the area between my sidewalk and the street. We have a lot of dogs in our neighborhood that pee along this grassy border.

AAny plant that can tolerate salts is likely to withstand dog urine as long as it is not too frequent and rainfall is sufficient to keep it diluted.

Rugosa rose, shore juniper and blue lyme grass are some plants that come to mind. Bayberry may also tolerate the abuse. All of these plants require good drainage, and while they can endure drought well, they will grow better if you give them a good soaking (with plain water) in times of drought.

I read about efforts to redraw the lines in the USDA Hardiness Zone map. I wonder if global warming may affect what plants we can grow here, with some warmer-climate plants surviving winters but trees and shrubs from northern areas not faring so well. I purchased two camellias and worry that they may not be winter hardy in spite of all the talk of climate change. Also, is it better to use cool-season varieties of grass, or should we all be switching to warm-season types such as zoysia?

It's too simplistic to think that global warming will result in drastic changes in what we can grow. This will be a slow process that will be limited to a large extent by extremes. Both global warming and the USDA Hardiness Zone map deal in climate as opposed to weather extremes. Temperatures may, on average, become warmer, but the extremes in temperature may be no different.

As this past winter bore out, global warming may actually make winter hardiness more of an issue. As the weather becomes more erratic, we may find ourselves going from a balmy subtropical spell to a significant cold snap in no time at all, and more frequently. I saw plants injured by 10 degrees Fahrenheit last winter that had not been injured by minus-10 degrees in the winter of 1995-96. Consistently cold conditions are not as hard on plants as wild swings from warm to cold and back.

Turf-type tall fescue is still the best choice for our area. Because we still have the potential to experience temperatures below 20 degrees on a routine basis, subtropical grasses are not a safe bet here. Fescues are considered cool-season grasses because most of their growth takes place during cooler periods of the year. Warm-season grasses are the opposite: dormant all winter and growing rapidly in summer's heat. Zoysia is the only warm-season grass that is reliably hardy in our area, and it has fallen from favor because it is dormant for such a long time, from October to April.

Scott Aker is a horticulturist at the U.S. National Arboretum.

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