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Bittersweet Invasion

Bill Meredith

"The only constant is change."
Heraclitus of Ephesis, ca. 500 BC

(October, 2013) We built our house about 25 years ago, and immediately had to face the problem of landscaping around it. This excited my wife; to her, it was an opportunity for shopping. I was less excited because I knew who would end up doing the work. Her excitement abated considerably when she saw the price tags on new plants; her usual approach of "if you’ve seen one plant, you’ve seen them all" took over. So it was that at one nursery she noticed a pile of half-dead potted plants that were available free. She assured me that, since I had taught Botany for 40 years, I would have no trouble making them grow, and we brought home a motley collection of them. Among them was a Japanese Barberry, which now stands by the east corner of the house, snarling at passing birds and daring anyone, man or beast, to come within reach of its ravenous thorns.

The Japanese Barberry was brought to America as an ornamental plant in the 1890s, and has now invaded forests all over the eastern part of the country. The Frederick Post recently ran an article about it; it grows rapidly, crowds out native vegetation, and creates a habitat for the ticks that transmit Lyme disease. It was a very interesting article, and it got me to thinking… first, about how complicated ecology is, and then about how often we have suffered the consequences of invasive plants and animals. Several years ago I gave a talk to a garden club, in which I listed 40 species of weeds from my garden; only nine of them were native plants. Invasive species, both plant and animal, are all around us. Everyone knows the classic examples… chestnut blight, Dutch elm disease, Russian thistles, kudzu vines, Japanese beetles, stinkbugs, cockroaches, rats, emerald ash borers, English sparrows, starlings, pigeons… you don’t have to be a biologist to fill a page with them.

I was aware of invasive species long before I became a biologist. As a small child, my father showed me pictures of multiflora rose in the Farm Journal. The multiflora rose is resistant to several root diseases, so it originally was brought to America in 1866 as a rootstock for grafting ornamental roses. In the 1930s it was being promoted by the Department of Agriculture as a living fence for farms, and it became the classic example of good intentions gone wrong. Botanists tested the seeds and found they didn’t germinate, so everyone assumed the multiflora bushes would stay where they were planted. They discovered… too late… that the seed coats of the multiflora fruits contain a chemical that prevents germination, but if the fruit is eaten by a bird, the grinding action in the bird’s crop destroys that chemical. So, when the seeds pass on through the bird’s gut and are dropped in the soil, they are no longer inhibited from germinating… and they do, with enthusiasm. It took a while to figure this out, and by the time it was understood, it was too late. My dad liked clean fencerows, so he never planted multiflora rose hedges; but they came to our farm anyway. He was not a profane man, but by the time I was in college he had joined farmers all over the country in cursing the Department of Agriculture.

Early last month, my wife and I went to Hagerstown for a Sunday picnic with friends. Since I was not driving, I was able to look at things more closely than usual, and I began noticing more as a result. The weeds along the sides of the road had not been mowed, and in its best Sherlock Holmes manner, my imagination remarked, "Aha! I perceive that the economy has not yet recovered, since the state lacks the money to cut the weeds back." But then I noticed that on the banks by the road, and in the adjacent woodlands beyond the reach of the state’s mowers even if they had been working, the trees were being overgrown by vines. I recognized them; they were the Oriental Bittersweet, an invasive vine that is well known for its ability to grow with such vigor that it smothers the trees it grows on.

The first time I ever saw Bittersweet was in the early 1960s, when I was starting my graduate research on the distribution of crayfish. I was walking along Toms Creek near Shank’s Mill, looking for places to collect crayfish, when I saw a vine with red and orange berries climbing up a small tree. I didn’t recognize it, so I took a piece of it to the lab and tried to identify it; it was represented in my reference books as a native plant. I made a mental note to get some and plant it; but we didn’t own a house yet, and by the time I finished at the university and was able to buy our own place, I had forgotten about it. Then, while driving toward Fairfield some 20 years later, I noticed bittersweet vines growing along the road. A little further research informed me that this plant was not our native American species; it had been introduced from Asia in 1879 as an ornamental. It was planted along road banks to prevent erosion, and spread from there, and it now grows all over the eastern U. S. The berries are quite attractive and often used as decorations around Christmas; they are poisonous to people, but not to birds, which spread them in their droppings. The vines have become so common that they are starting to kill native trees.

When I began studying ecology 60 years ago, it was easy to imagine that I was seeing ecosystems comparable to what had existed when the country was first settled. Of course I knew that lumbering and agriculture had changed things, but even my teachers believed it would be possible to preserve the original fauna and flora in areas like National Parks. It was a na've hope. Now, everywhere I look, alien species are crowding out the native plants I grew up with; and the communities of animals that depended on them are being forced to change also. The woods that now stand behind my house are full of mulberry trees and Tree of Heaven, both brought here in colonial times in the futile hope of starting a silk industry. There are few native wildflowers in my woods; the ground is covered with Japanese honeysuckle, which smothers smaller plants. The Bradford pears that were planted to shade the streets of local towns have spread to the countryside; in the springtime, their white blossoms outnumber our native dogwoods and serviceberries. And the invasion shows no sign of stopping; within the last 10 years English ivy has come to Emmitsburg, and numerous trees have been killed by it. Things are changing, and for those who remember what our ecosystem once was like, the future looks less certain as each day passes.

Read other articles by Bill Meredith