Seeking alternatives to invasive plants in Maine

Whenever I finish talking to a group of gardeners about the threat of invasive plants to Maine’s natural areas, one question is always left hanging in the air: “If I should not grow Norway maple [substitute Japanese barberry, burning bush, Oriental bittersweet, shrub honeysuckle, and so many others] in my garden, what can I grow that will offer a similar ornamental character?”

The newest addition to the Brooklyn Botanic Garden’s All Region Guide series, “Native Alternatives to Invasive Plants,” answers this question. It is an indispensable reference book for the environmentally conscious gardener.

Contributing author Janet Marinelli, well known for her work on invasive species, begins the book with two facts that, taken together, provide cause for concern about the impact of our actions on the environment.

First, we learn that biologists consider invasive species to be one of the two greatest threats to native plants and animals, second only to habitat loss from urban sprawl, agriculture and industrial development. Second, we are presented with the alarming fact that about half of the worst invasive plants currently degrading natural areas from coast to coast were brought here intentionally for horticultural use.

Marinelli reminds us that the history of horticulture in the United States is one of preoccupation with the new and exotic. But the more we learn about invasive species, the more we realize that the only prudent path is to avoid planting them in the first place.

This does not mean that only native plant species should be used in our gardens; non-natives that have been growing in our gardens for decades without escaping from cultivation – plants such as the common lilac – are good choices for our landscapes.

Still, the focus of this new book is on native alternatives to invasive species. For example, we can replace Norway maple (Acer platanoides) in our landscapes with red maple (A. rubrum) or, even better, black gum (Nyssa sylvatica), a native Maine tree that I have always loved, particularly in autumn when its leaves turn to flaming scarlet and purple-red.

We can replace Japanese barberry with our native bush honeysuckle (Diervilla lonicera), a multiseason shrub with clustered yellow flowers throughout the summer and autumn leaves of clear yellow to apricot and scarlet. Other recommended alternatives to Japanese barberry include summersweet (Clethra alnifolia) and bayberry (Myrica pensylvanica).

I was pleased to see that the authors listed burning bush (Euonymus alatus) as an invasive species. I have been convinced of its threat to Maine natural areas since working at an invasion site in Boothbay with one of my former graduate students. We need to stop growing this plant and there are several suitable alternatives, including highbush blueberry (Vaccinium corymbosum).

As I turn the pages of this book, I am struck by the fact that the choices we make when we select plants for our landscapes will determine the fate of the natural areas that surround our gardens. For more than a hundred years, those choices have been dictated by the nursery industry.

Indeed, many of the plants that we now know to be invasive threats are still being propagated, grown and sold. But the tide is turning. I am hopeful that future choices will be dictated by informed and environmentally conscious gardeners seeking regionally native alternatives to invasive plants.

Note: Copies of “Native Alternatives to Invasive Plants” can be obtained from the Brooklyn Botanic Garden’s Web site: http://www.bbg.org/.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to reesermanley@shead.org. Include name, address and telephone number.