Purple plant with a warning for all gardeners

Posted: 8 November 2011

An imported exotic plant is now causing explosive damage across the United States, and providing a warning to all gardeners, says Heather Parises in this report.

A field of purple plants waves all the way to the horizon and valleys full of this cat-tailed beauty can be seen standing strong and desirable in most wetlands of America – desirable in appearance, yet a huge nuisance at the same time.

Purple loosestrife
Purple loosestrife (Lythrum salicaria).

Standing 6-7 feet high, the purple loosestrife plant is an enticing perennial that was first introduced into the United States from Europe in the 19th century, and more recently by customers who bought the plant through exotic catalogues. But with each new growing season, this plant proved to be unmanageable for even the most seasoned green thumbs. People who let their gardens go unkempt have allowed this plant to escape and now a mass explosion is affecting most of the United States.

Professor James Pytko, an environmental geography teacher, explained that this plant is pretty common in the wetlands of Central Asia and Europe. This unruly plant has been seen in 48 out of the 50 states and is affecting marshes in Michigan.

“It was brought here as a garden plant because it has a pretty flower and people wanted to plant it in their yards. It got loose and got out of people’s yards, and it got into the natural ecosystems. That is why we have a problem with it now,” said Pytko.

Changing ecosystems

The purple loosestrife plant is affecting the population of its cousin, the winged loosestrife plant, by blocking the pollen receptors and not allowing the winged loosestrife plant to reproduce and multiply in the wetlands of the United States.

"The purple loosestrife plant is close enough related to the winged loosestrife that it can attach its pollen to the pollen receptors but it can’t make a pollen tube and fertilize. The purple loosestrife puts out so much pollen all at once that it coats the pollen receptors so the right pollen can’t get in there,” said Pytko.

Gardeners in the Great Lakes region do not realize the influence of the purple loosestrife plant and its lasting impact on the wetland ecosystem. It can change the entire ecosystem over time and wipe out the entire population of the winged loosestrife plant. All over our country this invasive species has affected nature and biomes.

Many people have sought out the purple loosestrife plant because of its resilient nature and ability to thrive in almost any environment. This has also affected people trying to get the purple loosestrife under control. Many attempts have been made to eradicate the plant from certain areas and this fruitless process is being hindered.

Purple Loosestrife map
Purple Loosestrife found in states shaded green.

The use of fires to wipe out the population is not an effective method because the roots lie too far under the ground and allow the plant to regrow after some time. Hand pulling the plants out of the soil is beneficial but only before the plant is 2 years old and before it sprouts its purple flower.

As the country realized the dangers connected with this plant, legal measures were put in place to limit the availability of the plant to consumers. In 1995 Michigan passed a law that prohibited the sale and distribution of the purple loosestrife. This has curtailed some of the problem and with the use of chemical herbicides some relief has been seen in the scientific community. However, this plant is still affecting such an enormous area of North America that not enough is being done to fully eliminate its grip on its surroundings.

Efforts have been made to root out young plants, take legal steps to limit its entrance into the country or sell it to consumers, and use of chemical herbicides on the plant. All of these together have taken with some success in Michigan to remove the purple loosestrife from surrounding wetlands, but there is much more to be done in this country and elsewhere.

“Gardeners never really thought about the impact of bringing in plants from all over the world. They need to think about that. We like to bring in strange new plants, but it’s not necessarily a good idea,” said Pytko.

Heather Parises is a senior year student at Central Michigan University.

For more information, see the US National Invasive Species Information Center.

 See also our page on Alien species.