Tuesday, April 28, 2015

Spring Green: Reading a Story of Forest Health

Spring, it is finally here. Even if you love winter, there is something about the warming days, gentle rains, and spring green that draws you outdoors or at least warrants a longing look out the nearest window.

Almost magically, we go from the brown gray fields and lawns to that fresh green, which is somehow vigorous and alive. A green that is much different from the green of June and July. Spring green, in its many shades, communicates a message of renewal and health.

If you are fortunate enough to have a forest or woodlot nearby, you can watch as the canopy takes on other colors and hues. A month or so ago you might have noticed tinges of purple, or, now, reds, yellows, and shades of green. This is truly a season of colors. Not the same bold all-encompassing colors of fall; rather, the soft pastels of spring.

Unfortunately, not all shades of green in our forests tell a story of health and vibrant renewal. Some of the early greens tell of unwelcome and health-robbing exotic invasive plant species. Many of these plants once occurred only in our yards and gardens; now they are increasingly dominating our forested landscapes and replacing more desirable native trees and understory shrubs and herbs.

The careful observer is aware that many of the early greens in our urban and forested landscapes are not our native plants. These early, and sometimes just as lovely, shades of green tell a story of changing plant health. Many of the most successful invasive plants have a physiological advantage over natives. Simply, they start to grow leaves earlier in the spring than do many native species.

Looking out my office window, it is easy to pick out the Norway maples in the neighborhood across the way. Already, they are sporting yellow-green crowns of flowers and young leaves, while the native maples, basswood, elm, and oaks are just beginning to show activity. The elms are brown-looking, the red maples are tinted red, and the sugar maples and basswood are still waiting to play their hands. In the woods, where Norway maple is becoming increasingly common, especially near our cities, the green really stands out early in the season.

The understory tells the same story. Some of the first plants to show their young, soft, green leaves are not native. If you know some of these plants, you will readily recognize that privet, bush honeysuckle, oriental bittersweet, and autumn olive are quick to green-up and gather in early spring sunlight before native trees begin to show leaves. These Asian plants also begin to green before native understory plants such as dogwoods and viburnums and by doing this being to express their dominance. Our native plants fall behind in the competitive race for water, nutrients, and light.

Should we care if these once friendly and invited guests from other places take over niches in our forests and woodlands? According to some researchers the answer is an emphatic yes. Physiologically, these plants have a jump on natives and because they are foreign to our landscapes, many of them do not host insects that would normally control, in part, their spread across our landscapes. These competitive exotic plants are not part of the ecosystem and they do not feed insects, which in turn feed other insects, amphibians, reptiles, and birds. In short, many of these plants do not contribute to forest health -- they actually take away.

The story of forest health and early spring green is complicated. If you take your time, you can learn to read this story on many landscapes. If you care, learn how to write a different story in coming springs. Work to control unwanted early spring green and plant natives in your yard and landscape. By doing so, you can still have spring greens, but know they represent a gift to others who benefit from and enjoy healthy forest landscapes.

Dr. Doug Tallamy, professor of entomology at the University of Delaware, has written a very informative book about the importance of native plants to our native insect and bird populations and what homeowners can do to enhance native habitat in their own backyards. "Bringing Nature Home," is an excellent addition to your library as you work to be a good steward of the land.

By Jim Finley, April 23, 2015

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