MADISON, Wis. -- About 150 Wisconsin landscape contractors held a conference at Olbrich Gardens on Friday to learn about how to install more rain gardens.

The meeting is part of a growing movement by both public and private groups to use rain garden to help replenish groundwater, control runoff and keep lakes and streams clean.

Rain garden experts said that landscapers could play a big role in controlling runoff by installing more rain gardens at homes and commercial developments.

When spring begins, landscapers will join a new effort focused on water and how to keep it clean, flowing and in the ground.

"It's a very hot topic. It's exciting. It's doing something good for the environment," said landscaper Craig Kittleson, of Kittleson Landscape, Inc., in Blue Mounds.

Experts said the rain garden has been gaining in popularity. It has been embraced by cities like Madison, where they've sprouted up along streets and in school yards and by some homeowners.

Experts said the theory behind rain gardens is simple: dig a shallow depression, fill it with prairie flowers and grasses, and it will collect runoff from roofs and concrete surfaces.

The garden can trap pollutants and recharge aquifers that go down as developments go up, WISC-TV reported.

The DNR said that's a growing problem.

"All over the state in urbanizing areas, the groundwater tables are going down and down. So we've got to get some of that water back in the ground," says Roger Bannerman, a water resource management specialist and rain garden expert for the Wisconsin Department of Natural Resources.

He and other water quality experts said that landscapers can play a crucial role in keeping the aquifers charged and runoff in check.

Experts joined a panel discussion on Friday, where contractors spent the day learning about the dos and don'ts of rain gardens -- from design, to installation and maintenance.

The industry interest is growing in part because of a new state rule that requires some kind of water filtration on any new developments that are more than one acre.

Landscapers said they're motivated but face some challenges. They said they're searching for answers and help from developers and others.

"(Landscapers) want to see it succeed just like everyone else. But I think there's a little bit more involvement needed in the chain from start to finish," Kittleson said.

Landscapers said that if developers get a better handle on rain garden costs and the state clarifies standards for them, they'll do their part to make the movement bloom.

One problem for landscapers is getting the right materials for rain gardens, such as good compost, WISC-TV reported.

The DNR said it hopes the industry will respond to that need so it can better control runoff where it's worst -- at big commercial developments.