AVERY COOPER: The Yakima River has a problem with water stargrass. It’s a native plant – but it’s choking the waterway and causing problems for people and fish. Now, machines are helping beat back the plant. NWPB’s senior environmental correspondent Courtney Flatt explains.

COURTNEY FLATT: In the summer, parts of the Yakima River are covered in green grass with yellow star-shaped  flowers. The explosive growth of water stargrass has degraded water quality over 50 miles of the lower river.

Crews are using two types of mechanical boats to remove the plant. Kristy Pentico is with the Benton Conservation District. She says – last year – she harvested 2-thousand pounds of water stargrass near Prosser, Washington, in a few minutes. This year?

KRISTY PENTICO: “We did not see much stargrass at all. We're thinking coupled with the floods in December and our aggressive harvesting last year.”

FLATT: The suppression strategy worked. But one type of boat just cuts the water stargrass instead of pulling it out by the root. Think of it like a lawn mower in a yard. But Pentico says the regrowth seems slower in some areas. 

I’m Courtney Flatt in Richland, Washington.