Feature Article February 20, 2003
LAND O' LAKES NewsWeb HomePurple LoosestrifeIn past articles Ive discussed three invasive species in our waters: Eurasian watermilfoil, zebra mussels, and water fleas. Gray Merriam, who also writes for the Frontenac News, sent me a note about the article on milfoil. He wanted to ensure our readers are aware that there are eight native species of milfoil in Canada. One of those is common in our region. He said, It would be unfortunate if enthusiastic 'controllers' applied their zeal to the native species. This leads to the issue of how to distinguish milfoil from other native genera such as 'coontail' (Ceratophyllum) and how to distinguish Eurasian milfoil from native northern milfoil. Exact separation gets technical but it is good enough to count the leaflets along one main leaf axis. For Eurasian it is 12 to 21, for native northern it is 5 to 9. Thanks, Gray. This week Ill discuss purple loosestrife, a common plant throughout our region. You can see its purple flowers massed in pastures and moist places from late June until the latter part of August. As you drive down the road, the fields of purple are quite beautiful. But there is a darker side to purple loosestrife. This perennial plant is native to Europe and Asia. It thrives in wetlands and disturbed areas. Purple loosestrife was first introduced to North America in the 1800's. Since then it has spread throughout the US and the southern provinces of Canada. In Europe native insects keep loosestrife in check. However these insects are not present in North America. Thus, lacking predators, the loosestrife spreads and chokes out other plants. Common native wetland plants, such as cattails and sedges, cannot compete. When they are gone, wildlife that depends on them for food and shelter also disappear. Purple loosestrife has little value as food for animals. It can form dense, impenetrable stands that are unsuitable as cover or nesting sites for a wide range of native wetland animals, including ducks, geese, muskrats, frogs, and turtles. he plant also invades the shallow waters used for northern pike spawning, ruining these areas as spawning grounds. Purple loosestrife flowers have five to seven narrow purple petals in long spikes at the ends of the branches. The stems are angular rather than round and are semi-woody at the base. The leaves are opposite or three in awhorl and do not have teeth. These features distinguish it from fireweed, which has round stems and flowers with four broad petals. Three control methods have been tried -- mechanical (hand pulling/digging), chemical (herbicides), and biological (insects are being grown and released against serious infestations of the weed). Physical removal and herbicides are only effective to treat very small areas. Many people also avoid chemicals because of their potential harm to the environment. Biological controls have shown more promise for large infestations. Biologists have experimented by releasing several species of weevils and beetles that feed on purple loosestrife in Europe. These have had a dramatic effect in decreasing the number of plants where they have been introduced. In one Ontario experiment, 500 beetles were released in localized stands and reduced purple loosestrife by 99%. The few remaining plants were overgrown by the native vegetation and did not produce flowers. Scientists are continuing their research into biological methods to control purple loosestrifea beautiful plant, but one that affects our natural environment.
