So what’s all this I hear about invading plants?

More and more people are embracing green philosophies. That’s great and I’d like to add one more for your consideration: Biodiversity, the variety of life forms, both plant and animal. Many consider biodiversity an excellent indicator of general ecosystem vitality.

When I was a teenager, I read a science fiction novel, Greener Than You Think, written by Ward Moore in 1947. It must have made an impression for me to remember it all these years. In a nutshell: a salesman tries a new inoculant, “The Metamorphizer” (an untested product that alters the structure of plants), on a ratty lawn of Bermudagrass (Cynodon dactylon). It works far too well. It creates a “Frankengrass” that grows wildly and takes over the planet.

It’s sci-fi but the message is real and way ahead of its time. Left to their own devices, invasive plants tend to create a monoculture, a landscape devoid of biodiversity.

Why is biodiversity important? Here’s one example. What if an invasive plant takes over and crowds out a native species that’s an important food source for a migratory bird? The birds may not get enough food to complete their migration and the reproduction of the species could be endangered as a result.

Less diversity means less varied habitat for wildlife. Invasives can also out-compete native plants for access to sunlight and the attention of pollinators. Butterflies can be fooled into laying their eggs on plants that kill or won’t support the larvae. Some invasive plants are even allelopathic; they can alter soil chemistry to discourage competition.

At Connecticut Gardener we hear about invasive plants and native plants on a regular basis, but the public is just beginning to get an inkling about what’s going on out there.

On a recent drive to Ithaca, it was depressing to see the same invasive plants over and over again: Japanese knotweed (Polygonum cuspidatum), purple loosestrife (Lythrum salicaria) and tree of heaven (Ailanthus altissima) were the most obvious from the road.

On the home front, you can walk down pretty much any street and see invasive plants in yard after yard. Japanese Barberry (Berberis thunbergii) and Burning Bush or Winged Euonymus (Euonymus alatus) are two of the most common. Alas, I sometimes get the “Are you from Mars?” look when I start talking to people about invasive plants.

Sadly, it’s no laughing matter. Barberry intrusions, for example, create an optimal environment for deer ticks. According to Scott Williams, a scientist with the Department of Forestry and Horticulture at The Connecticut Agricultural Experiment Station, “When we measure the presence of ticks carrying the Lyme spirochete (Borrelia burgdorferi) we find 120 infected ticks [per acre] where barberry is not contained, 40 ticks per acre where barberry is contained, and only 10 infected per acre ticks where there is no barberry.”

In other words, barberry-infested forests are 12 times more likely to harbor deer ticks carrying Lyme disease, a serious public health problem in Connecticut.

Japanese barberry is not banned in Connecticut because some cultivars are less aggressive than others. To their credit, the Connecticut Nursery & Landscape Association has voluntarily agreed to phase out the more aggressive examples.

And what about the financial cost? The California Invasive Plant Council estimates that invasive plants cost the state at least $82 million a year. Purple Loosestrife: Public Enemy #1 on Federal Lands, ATTRA 1997, estimated that purple loosestrife alone costs $45 million per year in control costs and forage losses. One estimate puts the total impact of all invasive species in the U.S. at $137 billion annually.

While the numbers are estimates, it’s obvious that the economic impact is significant. This is not an obscure matter of concern only to ecologists, land managers and foresters. It’s a big problem and it’s time for John and Jane Doe to be brought into the loop.

Often, people tell me their plant isn’t invasive because they see no evidence of it spreading on their property. Unfortunately, they’re not taking into account the fact that other agents (animals, high winds, water) may have distributed the seeds elsewhere. Humans can spread seeds on equipment and vehicles used by lawn crews, on clothing, and in mulch, potted plants, soil and compost.

Occasionally, people protest because some invasive plants are pretty. Purple loosestrife, Japanese barberry, burning bush and Oriental bittersweet are good examples. Yes, they are pretty, but they’re also detrimental to the environment.

So, what exactly are invasive plants and what makes them so bad?

According to the Connecticut Invasive Plant Working Group (CIPWG), “Invasive plants are non-native plants that are disruptive in a way that causes environmental or economic harm, or harm to human health. In minimally managed areas, invasive plants crowd out native plants. The presence of invasive plants alters the way plants, animals, soil and water interact within native ecosystems, often causing harm to other species in addition to the plants that have been crowded out.”

Invasive plants grow rapidly, reproduce quickly and can spread over wide distances. They’re prolific and often lack natural controls because they’re non-indigenous.

To make matters worse, our warming temperatures may bring us more invasive plants. Will kudzu (Pueraria montana), already present in Connecticut, take off in a warming climate?

And as if that’s not bad enough, there’s the whole issue of invasive aquatic plants, such as hydrilla (Hydrilla verticillat), and invasive animals, such as the Emerald Ash Borer (Agrilus planipennis). We can help spread these invaders when we move boats and firewood.

In Connecticut, the official group watching the issue of invasive plants is the Invasive Plants Council. The nine-member panel, created and governed by Connecticut General Statute 22a-381, makes recommendations to the state Legislature. It also publishes a list of invasive and potentially invasive plants. The official list, native alternatives, recommendations for eradication and other resources are all available on the CIPWG website at cipwg.uconn.edu.

What can you do to help? Consult the list, see if you have any invasive plants and remove them if you do. And, if you need a replacement, considering using a native. Native plants coevolved with local wildlife and they are interdependent. You can also assist local efforts to eradicate invasive plants such as Mile-A-Minute Vine (Polygonum perfoliatum).

Fortunately, the word is starting to get out. CIPWG hosts an Invasive Plant Symposium every other year. At the 2010 event, attended by about 400 people, one of the speakers asked how many people in the audience were aware of invasive plants in the 1970s. Only one or two people raised their hand. This year, the symposium will take place Oct. 25 at UConn’s Storrs campus.

For me, learning about invasive plants was a keystone of sorts that led me to consider more deeply how everything fits together. An awareness of invasive plants leads you to seek out alternatives. When you search for alternatives, you’ll discover biodiversity and the benefits of using native plants. Once you start down that road, you’re on your way.

Will Rowlands is the editor of Connecticut Gardener magazine (conngardener.com). He’s a UConn-certified Master Gardener, a board member of the Experiment Station Associates, and a volunteer member of CIPWG. He’s an award-winning journalist and designer, and a former board member of the New England Press Association.

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