Tending the Garden, Sparing the Ecosystem

By Joel M. Lerner
Saturday, October 11, 2008

Here's the test: How do you feel when you see a large slope planted with English ivy?

If you gasp in horror, you're in the vanguard of the native-plant movement. If you think, "How pretty," you might be aesthetically correct. But, from a practical standpoint, you may want to reconsider.

The plants and animals that naturally exist in a place evolved together, adapted together and coexist for mutual benefit. Birds, insects and other animals help pollinate plants and distribute seeds. Plants provide food and shelter for the animals.

When you start adding exotic or nonnative species, or subtracting native species, you disrupt the balance. Native creatures may not be able to get nourishment from nonnative plants, and indigenous plants may not be able to compete with invasive alien plants.

Another problem with nonnative plants is that some of them can escape. Even a well-tended garden can naturalize into the wild with the help of birds, bees, wind and a vigorous growth habit, driving out native species.

Norway maples ( Acer platanoides) are a prime example. The leaf looks like that of a sugar maple but without the magnificent fall leaf color and sugary sap. They are prolific seeders. One Norway maple can eventually colonize many areas of otherwise native woodland. The mixed, deciduous woodlands typical of the mid-Atlantic could give way to stands entirely of Norway maples, if we don't manage the woods and give time for slower-growing seedlings to dominate, such as oaks and hickories.

Russian olive trees, once used to control erosion, are highly invasive and damage habitat for wildlife. Purple loosestrife ( Lythrum salicaria and Lythrum virgatum) are garden plants that have escaped to colonize millions of acres of wetlands.

Faced with a 60-foot-long slope of English ivy, or a big Norway maple on your property, what should you do?

The simple answer is, rip it out, according to the Maryland Native Plant Society. "If you cannot effectively contain these plants within your property, by clipping seeds, fruits, or runners, consider removing them," according to guidelines on the society's Web site, http://www.mdflora.org/publications/invasives.htm.

Replace invasive plants with native shade trees such as white oak ( Quercus alba), red oak ( Q. rubra), Southern red oak ( Q. falcata) and mockernut hickory ( Carya tomentosa). Instead of English ivy, the native plant society recommends American bittersweet ( Celastrus scandens) or trumpet honeysuckle ( Lonicera sempervirens).

So, how do you get rid of these unwanted plants? The Maryland Native Plant Society offers the following suggestions.

In the case of Norway maples, there are a number of methods: pulling seedlings and digging out larger plants; cutting down the tree and grinding out the stump; clipping off sprouts and girdling the tree (cutting through the bark and the growing layer all the way around the trunk about six inches from the ground), which is most effective in the spring; hacking several holes into the growing layer and squirting in glyphosate, which is sold under many names including Roundup, Touchdown Total, Rodeo Herbicide and Glypro. Cut down the tree and paint the stem or stump with glyphosate, or paint the foliage with glyphosate following all labeled directions for a "wiper" method of application. This is most effective in middle to late summer.

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