Thistle Control

Asked September 22, 2015, 8:35 AM EDT

I'm treating a pervasive patch of Canada thistle with Home Depot's HDX and it is finally dying after several applications.
1. Do I need to reapply the HDX after each rain? We have had so much rain that I'm not sure if an application is going to be effective so I've been reapplying after a rain which is very time consuming and expensive. It takes 7 to 14 days to be effective and I'm not sure it's working since it's been rained on.
2. What do I do with the (seemingly) dead plant? Is it actually dead all the way to the root end? Do I pull it out, cut it off at the ground, or just let it lie? Will it regenerate if I don't get the root out?

Hennepin County Minnesota

1 Response

You should only need to reapply HDX if it rains within 24 hours of your application. Glyphosate is absorbed into the plant's vascular system through the leaves and then you may begin to see some result in a few days but you need to wait the full 2 weeks before you remove the plants. Once you are sure you see no sign of life in the plant you could pull up the plants along with the roots. I would suggest instead that you cut the plant off near the soil, disturbing the plant as little as possible. The plant is dead but the seeds are still viable. Bag the plants and dispose of them. This link goes to the product information:

http://www.homedepot.com/p/HDX-32-oz-Weed-and-Grass-Killer-Concentrate-HG-98024/203663674