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Duluth, Minn. — Debbie Braeu's backyard is canopied with trees, and the ground is blanketed with shade-loving plants. Water burbles over some rocks, into a pool about the size of a bathtub.
"There's a pump in the pond that recirculates, and the water comes down the stream, goes back up," she says. "As you can see, this is real close to our house. So we can sit and have coffee and we can watch the goldfish. And then we open the windows and we can hear the sound of the water, and it's really wonderful."
Braeu and her husband were on the front end of the water garden boom. They built this pond and stream 15 years ago. Since then they've helped lots of other water gardeners get started.
The Braues run Edelweiss Nursery just outside Duluth. They're big fans of native plants -- irises and water lilies that naturally grow in Minnesota.
They're careful in choosing exotic water plants. Some exotic plants die off in a Minnesota winter, but others can survive.
The Braues steer clear of plants that the Department of Natural Resources has labeled "invasive."
"But I think that people that are starting a business or just learning the ropes, they aren't aware of all these things," Debbie Braeu says. "So it's important that the retailer be educated."
Gretchen McDaniel nods her head and chimes in.
"That's why I went to the DNR Web site myself before I started this," she says.
McDaniel is helping the Braues rebuild some of their water gardens this summer. She just moved here, and she's trying to launch her own business selling water garden plants.
"I wanted to make sure I didn't do something stupid, because I came from Michigan, so I don't know what's a problem here," she says. "So I went to the Web site and I copied it off, and I keep it in my book so I know what's what."
That's the kind of thing Barb Liukkonen likes to hear. She's a hydrologist with Minnesota Sea Grant, and she's trying to slow down the spread of non-native water plants. She has a grant to educate people who sell plants for water gardens -- and people who buy them. She wants to encourage gardeners to use native plants, and she wants them to make sure the non-natives stay in the garden.
"There are a lot of invasive aquatic plants -- some that nobody would import intentionally," Liukkonen says. "Things like Eurasian watermilfoil, or curly-leaf pondweed -- things that cause a real problem in our lakes. But there are a whole range of plants that are being used for water gardens and to restore shorelines, that may also be very invasive. They're really pretty. Things like yellow iris, flowering rush, floating yellow heart -- plants that look good, but they can be very invasive."
Barb Liukkonen says exotic plants escape in at least a couple ways. Naive gardeners sometimes put the plants in a lake because they think they'll look nice. That's illegal.
And then there are hidden invaders. The State of Minnesota recently paid for research into aquatic plant-buying on the Internet.
"Ninety-two percent of time, the plants that are ordered had hitchhikers," Liukkonen says. "That is, unintended plants or animals or seeds. And those can be introduced when you plant those plants along your shoreline or into your water garden." The researchers found something else.
"When they ordered plants that were prohibited, that is illegal to own or to plant or to sell in Minnesota, they still received them 13 out of 14 times," Liukkonen says. "So even though they're against the law here, people can still order those plants."
Liukkonen says local greenhouses are much more likely to stay within the guidelines.
She and other staffers at Minnesota Sea Grant are testing some marketing ideas this growing season. They hope to go statewide with the campaign next year. They're printing up fact sheets that greenhouses can give to customers, and they're talking about designing plant markers that warn gardeners they're buying a non-native plant that could spread if it gets into the wild.