Wednesday, October 10, 2007

Invasive Plants

Two popular shrubs have become invasive in Pennsylvania dominating natural resources and depleting cover and food for wildlife – Japanese Barberry and Burning Bush.

Japanese Barberry (Berberis thunbergii) has never been a favorite of mine because of its sharp edges. It has a burgundy color that adds interest to the landscape so it is has become an attractive addition to many gardens.

According to Invasive Organization

“In the United States, Japanese barberry occurs throughout much of New England and the Northeast, south to North Carolina and west to Michigan and Missouri. Barberry forms dense stands in a variety of habitats, including closed canopy forests and open woodlands, wetlands, pastures, meadows and wastelands. This highly shade-tolerant exotic shrub displaces a variety of native herb and shrub species in areas where it is well established.”

The Barberry variety ‘Concord’ can be substituted providing everything the invasive plant offers without the seeds that promote invasiveness.

I do have personal experience with Burning Bush (Euonymus alatus). Purchased in the early 90’s, I wanted a shrub that would add some color to the fall landscape. I got the color but I also got hundreds of seedlings after the shrub matured. I’ve removed the bush.

The Global Invasive Species Team has this to say about Burning Bush:

“This new invader is becoming increasingly common in Connecticut, Virginia, Pennsylvania, and Illinois. It has been observed making dense thickets in Pennsylvania. These thickets can shade out native herbs and crowd out native shrubs.”

Some native plant substitutes for Burning Bush worth checking include: maple-leaf viburnum (Viburnum acerifolium), Korean spice viburnum (Viburnum carlesii), service berry (Amelanchier arborea), spicebush (Lindera benzoin), strawberry bush (Euonymus americanus) or red chokeberry 'Brilliantissima' (Aronia arbutifolia 'Brilliantissima').

Even the much loved Butterfly Bush (Buddleia) has become invasive in some parts of the country. Since seeds of the Butterfly Bush don’t mature until spring, trimming spent flowers in the fall will greatly reduce the threat.

It may take a bit of research to make the right choice when buying shrubs or working with a landscaper. But, by staying away from the shrubs that can become invasive, at least I won't add to the problem.

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