Roundup to kill invasive tree
I have a few large thorny locusts on my property that I would like to kill - for safety reasons. For those of you that have never seen one, they have thousands of 2-5" thorns from the base of the trunk to the tips of the branches. They are great for mower/tractor tires as well... I will likely wait to cut them down, but want to kill asap them to keep them from spreading - they are very invasive and often sprout via suckers and from spread of their seeds.
I've heard drilling holes in the trunk and filling with concentrate Roundup will do the job. Question is, should I do this in the fall or spring, or does it matter? I remember a converstation on this board about timing based on what direction the sap is flowing. Does it really matter that much?