Green invader: It came from the aquarium

Powderhorn Lake in south Minneapolis has a new inhabitant -- one city and state officials hope to eliminate this fall.

An invasive plant called Brazilian elodea, also known as giant elodea or Brazilian waterweed, has been discovered for the first time in Minnesota during a survey of aquatic vegetation in the urban lake.

Its source? Most likely a domestic aquarium.

The plant, native to South America, has bright green leaves and stems that grow 6 feet long or more. Commonly sold as an aquarium plant, it has spread to at least a half-dozen countries and numerous states, some of which have banned its sale.

Chip Welling, a scientist with the Minnesota Department of Natural Resources, said that the Brazilian invader is similar to Eurasian watermilfoil, which also grows rapidly on long stems, forms large mats on the water's surface and interferes with boating, swimming and native plants.

The plant is well-established in Powderhorn Lake and has survived winter there for at least one year, he said.

Previously, the plant had infested areas that for the most part have milder temperatures than Minnesota's.

"By comparison with Eurasian watermilfoil, we don't think it'll grow as abundantly in Minnesota," Welling said.

"But we can't say that with 100 percent certainty, and it would be ideal to get rid of it," Welling said.

DNR and Minneapolis Park and Recreation Board officials are forming a plan to eradicate the plant from Powderhorn Lake by using herbicides before it spreads to other lakes and streams, he said.

The chemicals may be used this fall, Welling said, depending on city approvals and weather conditions, with follow-up treatments next spring if needed.

The plant, which was discovered by Park Board limnologist Rachael Crabb, probably came from an aquarium that someone no longer wanted, officials said.

"If you dump the contents of your aquarium out, these plants and animals might live, and we really don't want them in the state's natural waters," Welling said.

He recommended that people who want to dispose of plants in their aquariums, ponds or water gardens either try to give them away or seal them in plastic bags and put in the trash.

Tom Meersman • 612-673-7388

Tom Meersman • meersman@startribune.com