Tree seedlings are easy to spot right now:
Any woody plant with foliage emerging in a garden is probably not wanted, but very easy to pull. Get them while they are less than 6 inches tall and they can be pulled by hand.
If they get any larger, use a channel lock pliers, to pull gently but firmly without cutting it off. I’ve successfully pulled hackberry seedlings that had 3′ of root without digging, by just gently pulling the base of the tree with that pliers. Nice long, padded handle. Can purchase in a variety of sizes that fit your hand.
– Douglas Owens-Pike, Metro Blooms Sustainable Landcare Expert