Alien Plant Invaders
Each year my family drives down the coast from Long Island, New York, to North Carolina to visit my grandparents. My earliest recollection of these trips was when I was six years old. At one point during the drive, I remember peering out the car window onto what seemed like a science fiction movie set. A green leafy monster had invaded the Earth and was devouring everything in its path. It draped eerily from the trees like a shroud, and the entire ground was smothered beyond recognition under the weight of its proliferation."What is that?" I asked my mother."Oh, that‘s an invasive vine called kudzu," she said. "It will continue to spread over the entire area unless someone stops it.""Could that happen in our town?" I asked fearfully.
"Well, yes, I guess it could," my mother answered. I had not yet reached the age of reason, but I knew that something was very wrong. For months to come, "Invasion of the Killer Kudzu Vine" was my nightmare of choice. Every morning I rushed to my bedroom window to see if any invasive plants had begun to overgrow my yard.
Now, 10 years later, I propose to find out if any of the top 20 non-native invasive plants in New York have invaded my yard in Cold Spring Harbor, New York.Non-native plants are those species that are not indigenous to a given ecosystem. An invasive plant is one that spreads quickly, decreasing the native plant diversity, causing local extinctions, and homogenizing the plant community. Invasive non-native plants are harmful because, according to Marilyn Jordan in Ecological Impacts of Invasive Species, they can change fundamental ecosystem processes such as decomposition rates, nutrient cycling, hydrology, soil chemistry, vegetation structure, frequency of wildfires, rate of soil erosion, and natural succession. Invasive plants are one of the major causes of decline for 42 percent of the U.S. species federally listed as endangered (Jordan, 2001).
Thirty-five percent of the 3,195 plant species in New York are non-native. Only 30 of these non-native species are reported to have invaded the surrounding native ecosystems (Jordan, 2001). The New York Invasive Plant Council (IPC) has identified the top 20 worst non-native invasive plants in New York as the Norway maple, garlic mustard, porcelain-berry, Japanese barberry, Oriental bittersweet, spotted knapweed, Elaeagnus species (Russian olive and autumn olive), Japanese honeysuckle, honeysuckle shrub (fly and Tartarian honeysuckle), purple loosestrife, Japanese stilt grass, Eurasian water milfoil, common reed grass, Japanese knotweed, curly pondweed, Rhamnus species (common and smooth buckthorn), black locust, multiflora rose, water chestnut, and black swallow-wort. The kudzu vine did not make the top 20 list, but is considered a potential threat to Long Island, where it has already been spotted growing in Suffolk County.
The IPC has documented the traits of invasive plants as including early maturation and reproduction, long flowering and fruiting periods, abundant small seeds, seed dispersal by animals, and a high percentage of seed germination. Other traits include high seedling survival rate, seed and vegetable reproduction, self-fertility, toleration of a wide range of biological disturbances, and the ability to thrive in various environmental conditions. Since these invasive plants are not native to the ecosystem, natural selection has not provided them with competitors, parasites, pathogens, or predators to keep their growth in check (Invasive Plant Council of New York, 2001).
Before my expedition, I contacted Tamson Yeh, Ph.D., Extension Educator at the Cornell Cooperative Extension. She provided me with descriptions and pictures of many non-native invasive plants in New York.
On Friday, October 5, 2001, I began the expedition in my backyard. It was 3:30 pm and a beautiful 70-degree day. My equipment included a camera, a pad and pencil for note taking, an envelope for specimen collection, plant descriptions, and mug shots of the top 20 invaders in New York. Since my yard is mostly woods, I decided to begin by examining the trees. After reading the description of the black locust (Robinia pseudoacacia), I knew right where to look. Three trees and many saplings along our driveway had all the characteristics: a tree up to a hundred feet tall, deep furrowed bark, and stout prickles on the twigs. The oval, smooth, margined leaves display themselves in leaves of seven to 21 leaflets. The alternate compound leaves were one to two inches long. These clues alone were not enough to substantiate my identification. The drooping clusters of fragrant white flowers that appear in May and June, later followed by thin, flat fruit pods two to four inches long, were the distinctive traits that confirmed these trees as black locust (Converse, 1984). It is noteworthy to mention that since it was October, neither the flowers nor the pods were present. It was my prior experience seeing these trees throughout the entire growing season that aided me in identification. The negative characteristic of an invasive can be a dead giveaway. The black locust is a member of the pea family and reproduces vigorously by root suckering. My father has been plagued for years by suckers from these trees sprouting in our gravel driveway.
The black locust is native to the southeastern United States on the slopes of the Appalachian Mountains. It was introduced into New York extensively for its hardwood lumber, its erosion-control properties, and to provide nectar for honeybees. The most effective form of control of this non-native invasive plant is removal of the tree, followed by a hand application of the herbicide Roundup, a glyphosate solution, to the stump (Heim, 1990).Although there were many species of trees in the woods, the leaves of the Norway maple (Acer platanoides) could not be missed. Just at the wood‘s edge were six trees with enormous leaves. A distinguishing feature of the Norway maple is its dark green, five-lobed leaf, which can be as large as eight inches across. Characteristically, when I tore a leaf from the tree, milky sap ran from the stem. These trees range from three to 20 feet high, although they can grow as large as 50 feet (Jiasvey and Allaire, 1998). Again, prior experience of viewing this plant was helpful in identification. Although the horizontal winged fruits were not present, I remember seeing hundreds of these fruits fall to the ground last spring. On October 5 the leaves had not changed color, but I can report upon writing this, three weeks later, that all the leaves have changed to a bright, golden yellow. This is the typical autumn color for Norway maple leaves. Viewing a plant during the entire year has proven to be enormously helpful in identification.
The Norway maple was introduced from Northern Europe. Fast-growing and easily transplanted, it was quickly planted throughout the East along city streets and in parks. Removal of a Norway maple is a large task. The 40- to 50-foot trees must first be cut back. Then the entire root system must be removed or the tree will re-sprout.
Next, I began to search for Japanese barberry (Berberis thunbergii). This was easy. I had trimmed my grandmother‘s Japanese barberry hedge many times and knew just what to look for. It wasn‘t long before I found two bushes set back in the woods 20 feet. Unlike the dense low hedges I was familiar with, these bushes were sparse and had grown enormous. Even in partial shade, the bushes were five feet high and six feet across—a testimony to their adaptability. The wedge-shaped, smooth-edged leaves, up to one and a half inches long; thorns; and red fruits cemented the fact that Japanese barberry has also invaded my yard (Jiasvey and Allaire, 1998). While it seemed odd to see a plant typically grown as a hedge growing wild in the woods, escaping from cultivation is one of the things an invasive does best! Japanese barberry was brought here from Japan as an ornamental (Jiasvey and Allaire, 1998). It is most effectively controlled by hand pulling.
Another fruit-producing, non-native invasive I found in my yard was the multiflora rose (Rosa multiflora). This thorny perennial, with large arching stems, had grown to a height of five feet and a width of four and a half feet. Along with leaves divided into five to seven sharply toothed leaflets, this invasive had clusters of showy fragrant flowers. The small red fruits were not present (Bergmann and Swearingen, 2001). This plant grows proudly in our sunny front garden. Although this plant is an invasive, my mother likes its flowers and regularly fertilizes it to promote growth. In my mother‘s opinion, this is an example of an invasive‘s desirable qualities outweighing the negative qualities. I think conservation botanists might have another view.
The multiflora rose made its U.S. debut in 1866. It was introduced from Japan as a rootstock for ornamental roses. Removing multiflora rose takes repeated efforts. One must cut the plant back six or more times per growing season to thwart growth. If this method does not work, an application of glyphosate must be used repeatedly to kill the plant and the long-lived stores of seed in the soil (Bergmann and Swearingen, 2001).
In my yard, I also found an abundance of the non-native invasive called Japanese honeysuckle (Lonicera japonica). Along a 30-foot stretch of land, this semi-evergreen vine crept three to four feet out of the wood‘s shade in search of sunlight. Identification was most accurately established by viewing the leaf structure of the plant. Japanese honeysuckle has leaves near the tip of the vines that are opposite and not united. Its fragrant, tubular, yellowish flowers were still present (Williams). Vegetative runners aggressively colonized the ground, while other shoots swarmed over understory plants and 15 feet up tree trunks. Japanese honeysuckle originated in Japan. It was planted in the U.S. for its ornamental qualities and was widely promoted by the U.S. Soil Conservation Service for the prevention of erosion. Hand-pulling small plants is an effective control. However, burning, or an application of glyphosate in the spring, is recommended for larger vines (Williams).
Since garlic mustard (Alliaria petiolata) gives off a strong garlic odor when the plant is torn, identification was easy. At 10 different locations in and along the wood‘s edge, I found these two- to three-foot-high biennials. These were the second-year plants, which have sharply toothed leaves. The white flowers and the fruits, called siliques, were not present (Owen, 2001). Upon further investigation, I discovered smaller first-year plants in the same areas. These plants were six feet high and had rosettes of kidney-shaped leaves. Since garlic mustard can produce 8,000 seeds each season, it is no wonder I found so many plants. Garlic mustard originated in Europe and Asia. It was brought here for medical and cooking purposes. Since 1868, garlic mustard has been an escape artist from Long Island herb gardens (Morisawa, 2000). Control of garlic mustard is difficult. Hand pulling combined with burning and the use of herbicides can prove effective. However, these methods may have to be repeated for five years to kill the seed bank (Morisawa, 2000).
I next went in search of Japanese stilt grass (Microstegiem vimineum). This proved to be difficult. There were so many grasses that I found identification impossible. So I went in search of help.I called the local office of the Nature Conservancy, and set up a meeting/interview on October 12, 2001, with Marilyn Jordan, Stewardship Ecologist. She was generous with her time and a real expert on the subject of invasives. She told me that invasive plants were second only to habitat destruction as a threat to native plants in our ecosystem. Marilyn went on to say that locally the Conservancy is trying to encourage hands-on weed control groups or weed-watcher teams. She also spoke of a National Weed Program that is expanding weed control and education. Future plans of the Conservancy include the development of a Weed Management Area. The purpose of a WMA is to facilitate cooperation among all land managers and owners to conduct invasive plant control in a common area. Marilyn then told me some distinct characteristics of Japanese stilt grass and showed me a specimen. There‘s nothing like seeing the real thing! I headed back to my yard feeling armed and confident with my newfound information.
When I arrived home at 5 pm, it was still light. I began to search immediately. To my horror, I found Japanese stilt grass everywhere! It was the annoying grass my father pulls out of the lawn, the dreaded grass that spilled out of the woods into our gardens, and the tall grass pushing up boldly through our pachysandra. In each case, the stilt grass had formed dense, monotypic stands that crowded out all other native herbaceous vegetation. One patch was one foot by one foot, while others grew to three feet by 10 feet. This annual grass has somewhat reclining stems with lime-colored, lance-shaped leaves four to five inches in length and one-half-inch wide. The spikes of flowers that emerge at the tips were not present yet. The inflorescence (flower display) appeared at the end of the stem or at the leaf axils (Tu, 2000). The grass grew equally well in shade or sun. Since one patch of stilt grass grows along the roadside in front of my house, I decided to find out what the local highway department‘s policy is on the control of invasives. David McLuckis, Assistant to the Superintendent, said the highway department has no policy in effect and that they are not dealing with the situation in any way.
Japanese stilt grass is native to Asia, Japan, Korea, and China. It made its first appearance in the U.S. in 1919 (Tu, 2000). This grass may have accidentally spread to the U.S. because it was used as a packing material for porcelain from China. Hand pulling is the best method of removal. An application of glyphosate can also be effective (Tu, 2000).Further searching revealed no other non-native invasive plants. The expedition confirmed that seven of the top 20 invasive plants in New York have gained a foothold in my yard!
Since New York was one of the first locations colonized in the country, and one of the largest ports in the U.S., it has always been a beachhead for plant invasion. It is not surprising that the state has more foreign species than any other state. Most of these species do not pose a threat to our native ecosystem. However, those non-native invasive plants that do, are silently degrading the environment. The public seems unaware that, inch by inch, these invaders are creating botanical turpitude in their neighborhoods. In a recent Newsday newspaper article, Marilyn Jordan, a conservation biologist with the Nature Conservancy‘s Long Island chapter, commented on the non-native invasive plant situation. She said, "It‘s really not just a problem. It‘s a crisis, a true ecological crisis. And it‘s one that not too many people know about.‘ "
Astonishingly, many of these invasive plants are routinely sold at nurseries. This underscores the community‘s ignorance of the problem. Lectures, pamphlet distribution, and newspaper articles on non-native invasive plants would aid greatly in educating the public on this subject. Government intervention is greatly needed in the form of weed mapping and weed control programs. The mapping of invasives in each yard in my neighborhood, and the education of my neighbors, could be my next expedition.Oh, remember the kudzu of my nightmares? Well, although I did not find any growing on my property, I did find some stealthily flourishing along the side of the road only one-eighth of a mile from my home. I pass it every day as I go to school, and you can bet I will be watching its every move!
Bergmann, Carol and Jil M. Swearingen. "Multiflora Rose." November 7, 2001. Plant Conservation Alliance, Alien Plant Working Group. Retrieved from the World Wide Web on October 4, 2001: http://www.nps.gov/plants/alien/fact/romu1.htm
Converse, Carmen. "Element Stewardship Abstract for Robinia Pseudoacacia." August 4, 1984. The Nature Conservancy. Retrieved from the World Wide Web on October 4, 2001: http://tncweeds.ucdavis.edu/esadocs/robipseu.html
Heim, James. "Vegetation Management Guideline: Black Locust." 1990. Illinois Department of Conservation. Retrieved from the World Wide Web on October 4, 2001: http://www.inhs.uiuc.edu/edu/VMG/blocust.html
IPC Invasive Plant Council of New York State. "Top Twenty Invasive Plants in NYS." August 2, 2001. New York Community Trust/Kraft Foundation. Retrieved from the World Wide Web on October 4, 2001: http://www.nysm.nysed.gov/ipcnys/
Jiasvey and Allaire. "Japanese Barberry." 1998. Web of Species, Wellesley College. Retrieved from the World Wide Web on October 4, 2001: http://www.wellesley.edu/Activities/homepage/web/Species/pbarberry.html
Jiasvey and Allaire. "Norway Maple." 1998. Web of Species, Wellesley College. Retrieved from the World Wide Web on October 4, 2001: http://www.wellesley.edu/Activities/homepage/web/Species/pmaplenorway.html
Jordan, Marilyn. Conservation biologist, Nature Conservancey, Long Island chapter. Interview by Katherine Jones. October 12, 2001.
Jordan, Marilyn. "Lessons from the Western Wildfires." Newsday. September 6, 2000.
Morisawa, Tunya Lee. "Alliaria Petiolata." June 2000. Wildlands Invasive Species Program, The Nature Conservancy. Retrieved from the World Wide Web on October 4, 2001: http://tncweeds.ucdavis.edu/esadocs/documnts/robipse.html
Nyboer, Randy. "Vegetation Management Guideline." April 2001. Illinois Department of Conservation. Retrieved from the World Wide Web on October 4, 2001: http://www.conservation.state.mo.us/nathis/exotic/vegman/thirteen.htm
Owen, Mike. "Garlic Mustard-Serious Invader From the East." May 26, 2000. Iowa State University. Retrieved from the World Wide Web on October 4, 2001: http://www.weeds.iastate.edu/mgmt/qtr00-1/garlicmust.htm
Relf, Diane. "Japanese Barberry." August 1996. Virginia Cooperative Extension. Retrieved from the World Wide Web on October 4, 2001: http://www.ext.vt.edu/departments/environhort/factsheets/shrubs/japbarbr.htm
Rowe, Pamela and Jil M. Swearingen. "Garlic Mustard." August 1997. Plant Conservation Alliance, Alien Plant Working Group. Retrieved from the World Wide Web on October 4, 2001: http://www.nps.gov/plants/alien/fact/alpe1.htm
Swearingen, Jil M. "Japanese Stilt Grass." August 1999. Plant Conservation Alliance, Alien Plant Working Group. Retrieved from the World Wide Web on October 4, 2001: http://www.nps.gov/plants/alien/fact/mivi1.htm
Tu, Mandy. "Microsteguem vimineum." August 2000. The Nature Conservancy‘s Wildland Invasive Species Program, Department of Crops and Weeds Sciences, University of California. Retrieved from the World Wide Web on October 4, 2001: http://tncweeds.ucdavis.edu/esadocs/documnts/micrvim.html
Williams, Dr. Charles E. "Japanese Honeysuckle." Department of Biology, Clarion University. Retrieved from the World Wide Web on October 4, 2001: http://www.dcr.state.va.us/dnh/invloni.htm
Copyright © 2002 American Museum of Natural History
More About This Resource...
Less than 1 period
Supplement a study of ecology with an activity drawn from this winning student essay.
- Send students to this online article, or print copies of the essay for them to read.
- Have them research one or more non-native plants that have been introduced into your region, reporting on what they learn about these plants' effects on the ecosystem.
OriginYoung Naturalist Awards