Since plants will not be actively growing when the roots are too cold. Post-emergent herbicides like Agrisel GlyPhoSel Plus Herbicide are going to work best when the air temperatures are between 55-85 degrees. Some products will have better cool-weather performance down to about 45 degrees.
No, you cannot use an herbicide such as Agrisel GlyPhoSel Plus Herbicide to kill a mature tree as a soil drench application. Any tree that is 20 feet tall (or more than seedlings, really) should be cut down carefully and correctly. You could then apply Tordon RTU Specialty Herbicide directly to the freshly cut stump to prevent regrowth. View the full product label to determine if this will meet your needs.
