Did you sign up for the Home Depot Garden Club newsletter last time I mentioned it? If so, you'll want to check your inbox for the latest email. In it you'll find coupons for B1G1 Trees and $4/1 Weed-B-Gon Concentrate!
If you haven't registered for the Home Depot Club yet, I highly recommend it. Just check the box for the Garden Club and any other Home Depot newsletters you're interested in receiving. I've received many other great coupons in the past, including B1G1 Houseplants and B1G1 Glad ForceFlex Trash bags.