kill a cherry?
I need to kill a ~20-year old black cherry tree without cutting it down, and without using anything toxic to me or my garden. The tree's roots have spread all across my backyard, under my garden (where it steals water and nutrients as it shades out my tomatoes) and any poison that spreads through the roots could eventually end up in my produce. I can girdle the tree; I can drill holes deep into the trunk below the girdling and fill with salt-- or Cuprinol? Or something else? Will that kill the roots, or will I have to keep cutting shoots all across the yard for the next several years? Is there a better way?
Cuprinol and salt are not registered herbicides, so we can not make recommendations like that. You can girdle or cut the tree down, but as you noted, you will have to chase the sprouts for a few years. Typically this is not too much of a chore. Using a glyphosate based herbicide as prescribed by the following links would be a bit more efficient in eliminating the tree.
Glyphosate seems to be quickly degraded by soils. In either case I would recommend removing the tree completely rather than leaving a dead tree standing.