Kids with guns take on Japanese knotweed

July 26, 2007

This summer, a group of 12 students are involved in the Columbia Estuary Environmental Education Program (CEEEP). Our main goal throughout our five week time period is to eliminate all of the Japanese Knotweed along Birnie Creek. We are also assessing this creek and determining the water quality and ability of the stream to support fish.

Japanese Knotweed is an invasive species of weed and comes from Eastern Asia. This plant forms in dense clumps along river/stream banks, and anywhere that is disturbed. It can grow in any kind of soil, no matter how poor it is and can grow up to two centimeters a day. Knotweed has large, green, oval shaped leaves with a stem that is hollow and looks like bamboo. Beneath a stand of knotweed is an underground root system called a rhizome network. New plants are produced by the spread of fragments of the existing plants.

Why is Japanese Knotweed a problem? It is because it can grow basically anywhere. It spreads very quickly along stream banks and overcomes other plant life. When it kills off all the other plants, it disturbs the fish's food source, making it a bad area for fish to spawn so when fragments of the plant float down a stream, the plant takes over all along it and destroys the fish habitat and other plant life.

Now, you are probably wondering what is going on when you drive by the Assembly of God church and see all of us walking around with needle guns and cans of spray paint. What we are doing is killing the knotweed with the method called injecting. We fill up the canister of the gun with an herbicide called AquaMaster. Then we insert the needle at a 90 degree angle either between the first and second nodes, or the second and third. When we squeeze the trigger, the gun releases five milliliters of the Aqua Master into the stem. After a couple of days, it will work its way down into the root system and start to spread. You will generally begin to see the results after a couple of days; the leaves will turn yellow and red and start to fall off. It takes about 30 days for them to really start dying.

If you have Japanese Knotweed in your yard and want to get rid of it, do not cut it or pull it out. By doing this, it will only make it worse. By breaking it, you are spreading fragments of the plant, which will eventually get into the ground and little shoots of the plant will start to pop up. There is no quick and easy way to kill this noxious weed. The best thing to do is just continually spray is with glyphosphate. This may take up to three years though to completely kill the plant.

We learned most of this information from the chemist Dr. Ron Crockett. He came and spoke to us on the very first day of the job. He demonstrated how to use the injection guns and taught us about the herbicide we were going to use. Thanks to him, we are now able to successfully kill the Knotweed along Birnie Creek.

Other than exterminating, our group is also surveying Birnie Creek. Surveying a creek is when we figure out its carrying capacity, take its temperature, take its oxygen level, figure out its flow, and examine its riparian zone. A stream's carrying capacity is the maximum amount of water that can fit in its flood zone. A creek's flow is how many cubic feet are flowing in it per second. And the riparian zone is all of the plant life on the edges of the creek. By surveying Birnie Creek, we are able to decide whether it is a good habitat for fish.

So far, we have found the upper part of Birnie Creek to be an excellent habitat for fish to spawn. But as you go to the middle and lower reaches of the creek, it is not that great. To be a good habitat for fish, the stream needs to have high oxygen levels, low temperatures (60F or lower), a lot of diversity in the plant life, a lot of shade/cover, some deep pools, and a rocky bottom. Upper Birnie Creek has all of this, but as for the middle and lower parts, it's not so good. In the middle and low parts the bottom is muddy, it is very open with no shade to keep the water cool, and Japanese Knotweed, along with tall grasses, is limiting other plants from growing over it, so the diversity is low.

Well, that's about as much information as I can give you right now, but if you ever see us walking around and have some questions, feel free to ask!

For more information on the CEEEP Project, call Karen Bertroch at 360-465-2414.