Spotted Knapweed in Missouri


The year of 2004 is when I first noticed the invasive plant I had never seen before.  This is what they now call Spotted Knapweed.  The phone company had laid miles of cable and buried all the phone lines in the county and we had a junction box “planted” or placed at the corner of the highway and dirt road.  Where they dug up and made a mess of the ditch the  phone company then hired out a company to spray wheat straw in the recently dug up soil.  I believe that is when we got our new plant from Europe kindly established.   This new plant grew stately and tall and was of a weird lime green and had many small flowers pink to purple in color.  Spotted Knapweed is a short-lived perennial that grows two to four feet tall and the leaves are rather spikey and sparse and grows on a hard, woody stem.   The weed blooms in mid-summer and the flowering bud is about 3/4 an inch long.   The weed reproduces by seed only and when those seeds drop expect approximately 1,000 or more seeds per plant.  Once the plant becomes strong and hardy expect to have around 5,000 seeds per square foot.   One more thing about this plant and it’s desire to take over… has a toxin or natural herbicide that will kill other plants in the area.   I sprayed the ditch on both sides of the dirt road the first summer I spotted this plant before it actually went to seed and that seemed to take care of them.  Now since the Missouri Department of Transportation has not done their part, the weed has taken over the highway ditch and has spread to my field west of the highway.  I believe some action or relief should be taken upon this mess by the Century-Tel phone company but I imagine noting will be done by them.  Every landowner needs to be very aware of this plant and keep it out of your pastures by chemically controlling it.  If you don’t keep it in check it will rapidly invade pastures and cause a sharp decline in your livestock forage.  You need to spray this invasive plant before it goes to seed and best before it flowers.  Several government agencies have been working together to control this plant with releasing seedhead and root borer weevils in 2008 and 2009.  As a landowner if you choose to pull these plants you need to wear the proper clothing and leather gloves because this plant could cause a skin rash or bad skin reaction.   Once you have bagged the troublesome plants be careful and make sure you are pulling them before they go to seed and burn the plant completely.   Just like the Dandelion plant, House Sparrows and European Starlings came over with the settlers and their survival rate is non-stop, I’m afraid the Spotted Knapweed will win the fight here too. 

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