Paul, if they're suckers, they might already have a decent root system. I received a couple of dormant suckers with a few roots attached, planted them in the ground, and once they broke dormancy they grew like mad. I tried the same thing with a couple of suckers on an Excel--dug down a couple of inches, saw they had a few roots (one much more than the other), cut them loose and potted them up. The one with better roots is leafing out along the trunk; the other died back quite a bit before popping some new shoots near the base. Anyway, it might be worth checking yours to see what kind of roots they already have.