I have two cottonwood trees I just today had taken out. Both were 30-40 feet, and needless to say the roots run the length of my 12,000 square foot lot. I will try the Karo syrup,triox and 2-4-D. I want all these roots dead, However I don't know if working at the stump will be enough or do I need to work from both sides in? Please help.