In article , Cat
writes

I take it heeling means firming around the rootball with my heel after
planting?

My understanding of 'heeling in' is a temporary measure of holding a
tree, shrub or perennial plant while it is waiting to be permanently
planted. The plant is placed into a shallow hole, the root-ball is
covered with soil which is firmed down with the heel, then it is given
plenty of water and hopefully priority in the planting programme.
--
Alan & Joan Gould - North Lincs.