Can scion wood be to big for bark grafting? I got a liberty on clearance from lowes last fall and have some scion the size of 5/8 copper pipe. It is definitely last years growth.
If your certain it's last years growth then it shouldn't be a problem as long as it's not bigger that what your grafting it onto. I would try to use something more towards the tip of the scion as that seems like a lot of growth to get to 5/8". Any pics of the scion and tree?
Sure you can use it. It is just not quite as easy to work with as the 1/4 -3/8" scion wood. I get some of that heavier caliper of wood on trees I have, but I just pitch the heavier stuff in favor of the sizes that I know work for me the best. You can also wedge graft with the heavier stuff.