When weeds start to take over the beauty of the landscape, often it’s time to kick out the herbicide. We have a serious knapweed problem in our yard that we’ve been chasing every season. For a decade, my husband, Grant, has diligently pulled this noxious weed on the hit list of many people who know the damage it does to the landscape, as well as mowing it constantly to try to prevent it from reseeding everywhere, but it just kept coming back with a vengeance. Although it has a pretty flower that resembles bachelor’s buttons, and bees love them, knapweed is not wanted around here. It actually sterilizes the soil around it preventing other plants from thriving, or even living in some situations, and reproduces exponentially. 

Weed killer

It was time to step up the efforts, so after consulting the country weed department, Grant broke out the heavy duty weed killer to gain the upper hand. The main application occurred last fall as prescribed by the weed guys. The plants tend to take up the poison better prior to dormancy making it more effective. But because knapweed is one of those plants that produces thousands (if not tens of thousands) of seeds that remain viable for years, new plants popped up this spring. So, he’s been out hitting them with the spray. 

He read the label and double checked with the experts to ensure it was okay. Although, when he sprayed within the foliage line of one of the cottonwoods he started from, it quickly showed signs of herbicide damage. The leaves are wilting badly. He contacted the company to let them know since it specifically states it shouldn’t hurt the tree. We’re anxious to learn what might have happened. While it’s not completely dead at this point, it will be interesting to see whether the tree pulls out of it or succumbs to the herbicide. 

Further damage

My beautiful pear in the backyard is looking poorly, too, although in a different way. The leaves are curling and are tinged with black in some areas. I’m afraid it might be fire blight as it was loaded with blossoms a week ago, which of course, were highly visited by the bees who are the primary carriers of the bacterial infection. I’m going to hold off to see what it does, but I have a bad feeling I will end up cutting it down like I did the 2 other pears. Last year my older one did fantastic throughout the season, then turned black seemingly overnight. Since I really want pears sometime, I’m going to have to research fire blight resistant varieties to see if there is any hope. 

There isn’t much to do about the fire blight situation. I wanted to let everyone know to be extra careful with the herbicides. It can be difficult to diagnose positive herbicide damage only due to the symptoms. Although, the correlation between the herbicide and the leaf curling and wilting on the cottonwood seems highly suspect. From now on, Grant will not spray within the foliage zone on the trees. It’s difficult to balance needing to eliminate a noxious weed with the protection of the existing landscape. But, there really was no other way to eliminate the knapweed. It’s just a shame about the collateral damage. Be careful out there!