Killing Cottonwood stumps and runners
Hello UAF Cooperative Extension,
I recently cut down several large cottonwood trees on my property and I'd like kill the stumps and roots so that runners do not emerge from the roots. What herbicide or other method would you recommend to accomplish this? Would a herbicide for this purpose make the soil toxic to other trees and plants? Please provide any available literature that would provide guidance. Thanks for answering my questions!
Your best bet at this point is to let the stump and suckers grow back through the season, and apply a foliar herbicide to the regrowth. You can't do an application to the stump because those need to be done right after the tree is cut down. If though you notice that the branches sprouting from the cut stump are high enough that you could cut it again then you could do a cut stump application. He
re is some information on cut stump applications https://www.aces.edu/blog/topics/forestry-wildlife/cut-stump-herbicide-treatments-for-invasive-plant-control/
If the cut stump application won't work then your options are to apply an herbicide to the foliage. I would wait till you have substantial foliage, so probably the end of summer, because you need enough leaves to get the right dose of herbicide to the roots. You could also try cutting back suckers all summer long. Theoretically this starves the roots, but in practice I have heard people just get tired, or miss cutting when away on vacation leading to failure.
As for toxicity if you are careful and follow label instructions you shouldn't have any problems. To fully answer that questions I need what other desirable plants are growing in the area, or you intend to plant so I can determine if they are sensitive to an herbicide that you might use.