Coles County Yard and Garden

Coles County Yard and Garden

Invasive Exotic Plants

This column was written by Jon Collins, Coles County Master Gardener.

Anticipation grows as Christmas approaches, but in two short weeks the holidays will be over. In its place - the January blahs. That is unless you are a gardener. The anticipation remains for the gardener as the spring garden catalogues begin to arrive.

It's the same every year. That first magazine arrives. We sweep it up with growing expectations; quickly fix a steaming cup of coffee and rush to settle into some comfortable chair in a warm, bright corner of the house. Past that shiny, slick cover awaits the magical world of possibilities. Seeds and plants spill from the pages – new introductions, old favorites, plants we finally want to try this season (if only we can find a vacant spot). Check the hardiness, is the sun light sufficient, will it need extra watering. Oh so many things to consider, but somewhere in those pages is the perfect plant for that void between the Azalea and the Viburnum, if only we are diligent.

In our diligence to make sure it will fit into our garden, we need to keep in mind another factor. Does it have the potential to escape our landscape and become a pest in our native prairies and forests.

The nursery industry in its attempt to continue to bring the consumer new and exciting plants has increasingly turned to non-native and exotic plants to meet the demand and that has caused problems.

According to Ecologist Daniel Simberloff of the University of Tennessee, introduced species are a greater threat to native biodiversity than pollution, harvest (agriculture, forestry, fisheries), and disease combined. Compared to other threats, invasive introduced species rank second only to habitat destruction, such as forest clearing. Of all 1,880 imperiled species in the United States, 49% are endangered because of introduced species alone or because of their impact combined with other forces. Finally, damage to the U.S. economy inflicted by introduced species is estimated at $137 billion per year.

While much of this damage is caused by exotic animals, insects, diseases, or weeds brought into this country unintentionally, introduced horticultural plants have also contributed to the problem. An example of one that has gotten considerable news coverage in the last couple of years is Kudzu (at one time proclaimed the 'agricultural miracle' plant). This vine of the "southern" states that grows a foot a day and can completely cover everything 60 feet in all directions in one year, has been found in 30 counties in Illinois. While most colonies found are in the southern third of the state, one colony has been discovered growing as far north as Evanston.

Another well documented example is Lythrum – purple loosestrife. It was available in the nursery trade up until January 2001 when it was declared a noxious weed. This plant is present in Illinois predominately in the northern part of the state where it crowds out native wetland plants to create a monoculture that provides little food or shelter to native wildlife.

Want some examples closer to home? Exotic buckhorn. This shrub or small tree is filling the understory of the small woods behind the Physical Plant at Eastern Illinois University. Illinois has 3 native buckthorns, but the exotics from Eurasia (Common, Glossy, and Dahurian buckthorn) are causing the problem. These are still sold by some nurseries for use as hedges in many urban areas.

Another that I consider even more prolific and destructive are the exotic bush honeysuckles (fragrant, Morrow's, Standish's, Tartarian, European fly, and pretty honeysuckle) . These have been sold as ornamental bushes and as wildlife cover. Growing along the bike trail east of Charleston (probably Tartarian honeysuckle) , they have spread rapidly in just the last 3 years, overtaking whole areas with a dense shrub layer that crowds and shades out everything else.

The Global Invasive Species Database lists 88 invasive species in Illinois. Of these 52 are plants. I was surprised by some of the plants on the list. These are plants we have been using for years, but have now been found to escape the garden and are causing destruction to our native habits. Here are some you might be familiar with: Norway maple, chocolate vine (Akebia), porcelainberry, Japanese barbary, Asian bittersweet, cinnamon vine, Russian and autumn olive, winged burning bush, wintercreeper, English ivy, yellow flag (yellow iris), Chinese honeysuckle, Japanese spirea and periwinkle.

What can we do? Prevention is the best remedy. Don't plant any varieties that are known to escape our gardens and rely more on plants native to our area. Native plants are in sync with the existing environment. They will have fewer insect and disease problems, require less water, and will handle our cold winters and hot, dry summers better.

We must be good stewards not only of our own gardens and communities, but also of the native habitats surrounding our communities.

This column is based on information and materials available at the U of I Extension office, located at 707 Windsor Road, Suite A, Charleston, 61920. Master Gardener volunteers are available on an "as needed" basis during the winter months. If you have any questions about yard, garden or indoor plant care, write the office or call 345-7034.

Jon Collins Master Gardener & EIU Supt. of Grounds

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