Invader from Canada on noxious weed list
June 25, 2008 · Updated 12:12 PM
"Photo: Strong, bold and armed to the teeth, Canada thistle is a non-native weed that will quickly take over if left uncontrolled.There are few weeds as ominous looking as the Canada thistle. With prickly spines jutting aggressively from its leaves, stem and even its blossom, the thistle looks like a villain from a Road Warrior movie.And just like such villains, it's hard to kill.About the only good thing you can say about Canada thistle is that it's not poisonous said Gloria Wahlin, noxious weed coordinator for Island County. Wahlin said it's important to get rid of the invasive plant when you see it or you will most certainly see a lot more of it.In fact, both the state an county actually make it mandatory for property owners to control it. That means pulling it, cutting it, covering it, spraying it, or feeding it to animals or bugs.These days, the thistle is easily seen in pastures, along roadsides and even in residential yards. Its bright purple flowers are one of the first things you notice and from a distance the cheery color actually makes them somewhat attractive.But Wahlin said the flower is getting ready to produce a pile of seeds that will soon be carried by the wind to other locations. Meanwhile, below ground the plant is spreading its huge root system out as much as 19 feet horizontally and up to 22 feet down. As a result, one plant can quickly become a colony.What to do?The best way to control the weed is to mow it repeatedly either by hand or with a large mower or string trimmer.Of course you have the added labor of gathering up the cuttings if you think the thistle heads are developed enough to set seeds, said Wahlin.It's best to start mowing around mid May and keep cutting it down all season. But if you're getting a late start like a lot of people, there's still time to whack on it before it goes to seed. The best time to do that is right now.Thistle can also be controlled by pulling it but it's important not to till the ground afterward or you may spread parts of the stem that can resprout. After pulling, cover the ground with heavy plastic, wood, carpet or other material water can't get through and leave it in place for at least two years. That's right, two years - thistle is a pretty mean weed to be sure.Chemicals marketed under the names Curtail and Stinger are effective against Canada thistle and are approved by the Pacific Northwest Weed Control handbook published by Washington State and Oregon State universities. But, as with any chemical, it's important to read the instructions carefully to make sure you're not harming other parts of the environment. It's also advisable not to use chemicals around crops.Another organic method to control the weed are by using goats, which find thistle a gourmet delight. But Wahlin said you have to be careful about using goats for control because the animals also like to eat many other plants and can do more harm than good to a garden space.You can also use certain types of bugs such as the Canada thistle bud weevil, the stem weevil or the thistle stem gall-fly which weaken or strategically damage the plant.County officials have already released such thistle-eating insects throughout the island in hopes they will provide much-needed natural control of the non-native weed.If you have Canada thistle growing on your property and want more information call call Wahlin at 321-5111, extension 7211. It's also a good idea to look for the weed on neighboring property. Knowing the thistle's aggressive tendencies, it's likely headed your way."