Native plants are very much in fashion now for a variety of reasons. We assume their adaptability to a certain area makes them easier to grow and maintain. Ideally they take less water and fertilizer, and suffer less from our heat, humidity and sometimes cold weather than the exotics.
Those are among the reasons for many gardeners' turning to native plants.
But Carl Whitcomb, landscape ecologist from Stillwater, Okla., posed an interesting question when he addressed a recent symposium sponsored by the University of Florida/Hillsborough Cooperative Extension Service:
"Is any plant native to our urban environment once soils become homogenized and modified with all sorts of construction debris?"
His definition of "native" is simply that a plant was not placed by a human at a particular site. To be native, a plant found its own way and used its own devices to survive.
"And there is a difference between just surviving and actually flourishing," he explained. "We want our landscape plants to flourish, not just barely get by."
A site's circumstances are always changing, whether because of man or weather. Plants come and go as the conditions change. Dig down through the layers of soil and you will find fossilized "native" plants that are no longer growing there because of man-made or natural disturbances.
Whitcomb suggests that we look at a plant's tolerance and "manners."
"In order to have successful plantings on highly disturbed urban sites, we must look to plants with a wide range of tolerance," he said. This usually includes both natives and non-natives.
A plant with "good manners" will not produce invasive seeds or rhizomes, is easy to maintain, grows well in a wide range of conditions, and may be nearly pest- and disease-free, Whitcomb said.
The fact that a plant is growing native under certain conditions does not mean that it is at its best, he explained. "It simply means that it is able to tolerate the current conditions and survive."
Whitcomb maintains that relative to evolution, the species may be new and could become more vigorous and aggressive as conditions become more favorable; or it may be on its way out because it reached its limits of tolerance. It may even become extinct.
In Whitcomb's view, it would "be simplistic and foolish to plant only natives." He recommends a combination of native and introduced plants, with a focus on using whichever "good-mannered" species are best adapted to the site, regardless of whether they are considered native.
When I plan or renovate a landscape, I have trouble thinking on a "global" scale. But Whitcomb makes some good points. I prefer to use a combination of natives and non-natives that have grown successfully in this area for a number of years.
We have altered our _ and the plants' _ environment so much that I'm not sure it would be possible to use exclusively native plants. Some of our most attractive and widely grown plants, such as crape myrtle and India hawthorn, are not native to our area, or even our continent.
We need to be mindful of our limited water and work toward decreasing our reliance on chemicals for vigorous growth and pest and disease control. Carefully choose plant materials that will need the least amount of care once established.
I guess that does mean choosing plants that are tolerant of a site and have good manners.