"Pretty" Purple Plants Can Be Pesky

During the summer, many people notice the pretty purple-flowered plants along roadsides, in ditches and fields, especially in wet areas. But, that pretty plant can be very invasive and damaging to other wetland plants, which can reduce the effectiveness, diversity and ecological balance of the wetland area. The plant with the beautiful purple flowers is purple loosestrife. Those flowers eventually turn into enormous quantities of tiny seeds that get spread throughout the wetland and can create a seed bank that will last for years to compete against the native plants.

Purple loosestrife was introduced into North America in the 1800's and into Illinois in the mid-1900's. It has only become a real problem in the last 20 to 30 years. The plants can become 4 to 6 feet tall and have massive root and stem systems. High densities of purple loosestrife can create heavy mats that native wetland plants cannot compete with effectively. The loss of native plants can eventually mean the loss of native wildlife in the area and possibly even a reduction in the natural ecological effectiveness of the wetland.

Many types of controls have been used, but methods such as mowing, weeding, burning or using herbicides have not been effective on large scale areas and may be too labor intensive or costly. The problem is the millions of seeds left in the soil when plants are allowed to reproduce can send up new and more plants year after year.

Researchers at the Illinois Natural History Survey (INHS) in Champaign are currently evaluating biological control of the weed through the use of beetles that are natural enemies to the plant. The method has shown to be effective in many parts of the state, at least in small infestations. Although it may present a challenge to rid the state of the weed, this biological method appears to have long-term viability.

For landowners and others, the main consideration is to not encourage and enable the spread of the plants. Do not move plants from one location to another. Try to control small patches early by eliminating seedheads, or other control methods. Monitor the spread of the plant in the area and report significant increases to the survey researchers.

For further information, check the INHS purple loosestrife website at http://www.inhs.uiuc.edu/cbd/loosestrife.

August - September 2002:

"Pretty" Purple Plants Can Be Pesky
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