A 50 foot frazier fir or blue spruce is a beautiful tree there are others on my property that will be left alone. I'll bet you didn't plant a couple thousand 2-3 feet apart....that's where the problem is. :)
I fully expect to see all kinds of unwanted "things" sprout......sprayer will be ready.
Thanks for the advice and comments.
Be sure to get on them REALLY quick, but wait long enough to make sure that they aren't natives or "good things" coming up. I'd almost look into making some type of wiper to make sure you get great coverage.
You might be pleasantly surprised if you frost seed clover or SOMETHING into this space. Since it's been canopied for a good 20 years, a lot of seed in the bank will have lost its viability. My neighbor frost seeded white clover into a shooting lane similiar to this. Some of the best clover I've ever seen, and hardly any weeds.