Stacy wrote:
It's a small batch Alder trees that once established they just go wild and,
considered more like a weed in the Norhwest.

Is there a product on the market where I could snip them young and rub
something on the cut area and have it affect ***only*** its own root system?

I've haven't used it for that purpouse myself (although my father has),
but if it's not against your ethics, you could consider using a
glyphosate (Roundup) based herbicide. Instead of indiscriminately
spraying it on everything, you use gloves to rub it on just the leaves
of the plant you want to kill. If you don't drip it on everything, it's
effect should be limited to that plant.

Be aware that Roundup has warnings about it's effect on fish & other
aquatic life. But if you use the glove trick, and only apply if the
weather is going to be dry for the next day or two, you should be fine.