Q: How do I kill very large stumps that have been cut down to ground level?

A: If you need to keep the stumps from resprouting, chop into the edge of the stump with a hatchet and spray glyphosate (Roundup, etc) or triclopyr (Brush B Gon, etc.) into the freshly cut wound. The chemical will be sucked down into the vascular system of the stump and will prevent sprouting in the future.