Thank you for your comment! I wanted to address this point in more depth in my blog post, but I was working with a word limit constraint, so I am happy you brought this up.
As you pointed out this is a hotly debated topic and an agreement regarding the safety of glyphosate to humans and the environment has not been reached. In the meantime, glyphosate has certainly been both overused and irresponsibly used. However, there are a few instances when I feel its use is warranted, and one of these is for Canada thistle.
Unfortunately, because Canada thistle roots can reach depths of 6-15 ft (https://wric.ucdavis.edu/information/natural%20areas/wr_C/Cirsium_arvense.pdf), and also because it reproduces vegetatively, eradication of this weed can be very difficult. Gardeners can spend much time pulling the plants, but since much of their biomass is underground, Canada thistle often grows back. As for vinegar, it will kill the leaves of the plant as it damages the cuticle, but it is not translocated into the root system. As far I know, no organic herbicide is. Sure, elbow grease and the use of vinegar stress the plants out, so they are good tools to include in an integrated pest management (IPM) approach for Canada thistle. Which brings up a good point: if herbicide is used, it should only be used in combination with other IPM methods.
One thing I suggest is that if gardeners do choose to use glyphosate, they should apply it in a very targeted manner. Thus, instead of spraying plants I advocate for using a paintbrush to apply glyphosate to the leaves of Canada thistle. Of course, gardeners should follow the directions on the label too.
Finally, glyphosate should not be a long-term solution. It should only be used as the means to an end, which is to create a healthy, productive, biodiverse landscape. A personal example is that several years ago I inherited a Canada thistle infestation in my yard. I quickly became obsessed with getting rid of it. For two years, at the beginning of the growing season I would take scissors and cut back each individual Canada thistle plant to the ground. Towards the end of the summer I applied glyphosate each time a rosette emerged. I then mulched any areas that I was not immediately going to landscape. Other areas I landscaped with a wide diversity of Plant Select plants, Colorado natives, and other plants that thrive in our arid environment.
The Canada thistle has been eradicated. Because I stay on top of weeding and I am constantly monitoring for new infestations, I doubt that I will need to use glyphosate in my front yard ever again. Thus, I see glyphosate as a one and done tool in part of my toolkit for Canada thistle management, which helps me achieve my goal of creating a healthy landscape sooner.
I am excited about the prospect of other controls such as Puccinia punctiformis, which I mentioned in my blog, as it has the potential to effectively control Canada thistle infestations (and thus, decrease the use of glyphosate as a method of control), but that is another topic...
Thanks again for your comment and happy gardening!
Hi Gianna,
Thank you for your comment! I wanted to address this point in more depth in my blog post, but I was working with a word limit constraint, so I am happy you brought this up.
As you pointed out this is a hotly debated topic and an agreement regarding the safety of glyphosate to humans and the environment has not been reached. In the meantime, glyphosate has certainly been both overused and irresponsibly used. However, there are a few instances when I feel its use is warranted, and one of these is for Canada thistle.
Unfortunately, because Canada thistle roots can reach depths of 6-15 ft (https://wric.ucdavis.edu/information/natural%20areas/wr_C/Cirsium_arvense.pdf), and also because it reproduces vegetatively, eradication of this weed can be very difficult. Gardeners can spend much time pulling the plants, but since much of their biomass is underground, Canada thistle often grows back. As for vinegar, it will kill the leaves of the plant as it damages the cuticle, but it is not translocated into the root system. As far I know, no organic herbicide is. Sure, elbow grease and the use of vinegar stress the plants out, so they are good tools to include in an integrated pest management (IPM) approach for Canada thistle. Which brings up a good point: if herbicide is used, it should only be used in combination with other IPM methods.
One thing I suggest is that if gardeners do choose to use glyphosate, they should apply it in a very targeted manner. Thus, instead of spraying plants I advocate for using a paintbrush to apply glyphosate to the leaves of Canada thistle. Of course, gardeners should follow the directions on the label too.
Finally, glyphosate should not be a long-term solution. It should only be used as the means to an end, which is to create a healthy, productive, biodiverse landscape. A personal example is that several years ago I inherited a Canada thistle infestation in my yard. I quickly became obsessed with getting rid of it. For two years, at the beginning of the growing season I would take scissors and cut back each individual Canada thistle plant to the ground. Towards the end of the summer I applied glyphosate each time a rosette emerged. I then mulched any areas that I was not immediately going to landscape. Other areas I landscaped with a wide diversity of Plant Select plants, Colorado natives, and other plants that thrive in our arid environment.
The Canada thistle has been eradicated. Because I stay on top of weeding and I am constantly monitoring for new infestations, I doubt that I will need to use glyphosate in my front yard ever again. Thus, I see glyphosate as a one and done tool in part of my toolkit for Canada thistle management, which helps me achieve my goal of creating a healthy landscape sooner.
I am excited about the prospect of other controls such as Puccinia punctiformis, which I mentioned in my blog, as it has the potential to effectively control Canada thistle infestations (and thus, decrease the use of glyphosate as a method of control), but that is another topic...
Thanks again for your comment and happy gardening!