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A volunteer holds flowering rush after it's been pulled from the Columbia River.

I am betting flowering rush is a weed you have never seen. And hopefully, you never will see it. The only way to stop the spread of noxious and harmful weed is to be able to identify it and to change our outdoor habits.

As many other noxious weeds, flowering rush, Butomus umbellatus, was introduced on the East Coast as an ornamental for people’s private ponds. With attractive pink flowers, who wouldn’t want this growing in their pond? The problem with introduced plants is that their natural controls are missing in the new environment — and people are usually unaware of the growth habits and misbehavior of a lovely new garden plant!

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Don't let the pretty pink blooms fool you — the flowering rush is a Class A noxious weed in Washington state.

Rushes are distributed worldwide on the banks and in the shallow water of flowing streams and rivers — remember the biblical story of Moses being hidden in a basket in the bulrushes on the banks of the Nile? The reason that rushes occur so widely is that they evolved several ways to distribute their seed and to expand their territories.

The flowering rush produces seeds that float on the surface of the water and can be carried by the wind. The flower stalks also produce little bulblets that break free and float away to form more plants. More insidiously, the plant is anchored in the soft muddy shallow water with long, tough rhizomes (specialized roots that store food for the plant). In addition, more bad news, the rhizomes produce little bulbs that break free when the roots are disturbed and float along the bottom of the water until they lodge in a place where they can root themselves.

So why are we concerned about this plant invading our waterways? The flowering rush can compete with native wetland and shoreline plants, and it can crowd out native species. Worse, the rush provides hiding places for Northern Pike, a fish that lies in wait and ambushes salmon and other fish species.

According to the Washington Noxious Weed Board, Public and private landowners are required by state law to eradicate this plant when it occurs on their property. Flowering-rush is a Class A Noxious Weed in Washington due to its limited distribution in the state and the potential for significant impact to state resources.

The plants have a cylindrical stalk, up to 5 feet tall, ending in a flat-topped flower cluster with individual flower stalks originating from a common point of 20 to 50 light pink flowers. Flowers have three sepals, three petals, nine stamens and pink pistils.

It has a rhizome — a thick root — that produces thin, upright leaves that may be twisted in growth and reach 3 feet or more in length. They can be emergent, submersed or floating. Leaf bases are triangular in cross-section.

It is the bulblets that break free when the rhizomes are disturbed that allow the plant to infest areas downriver.

About a dozen of these plants have been found in the Orondo boat launch area and Turtle Rock, which is downstream of the Orondo infestation. They were removed in four successive years at a cost of nearly $8,500. Divers have been hired to remove the plants and use a suction hose to ensure that they have captured all the bulblets. Then a type of bottom barrier was secured to prevent any new germination of rhizome pieces. Boat surveys coordinated by WSU Extension, the state departments of agriculture and ecology, and the Chelan County Noxious Weed Board have been conducted annually to search for new infestations.

When you are enjoying the river this year, keep an eye out for this plant. If you see it — most likely be just a few plants in any location — contact WSU integrated weed management specialist Dale Whaley at dwhaley@wsu.edu.

A WSU Master Gardeners of Chelan County column appears weekly in The Wenatchee World. Bonnie Orr is one of four columnists featured.