3,572. New Growth From a Cut-Down Tree
Hilchos Maaser Sheini and Neta Revai 10:13
If a tree is cut down above the ground and a new one grows from it, it is obligated in orlah, counting the three years from when the original tree was cut down.
Hilchos Maaser Sheini and Neta Revai 10:14
Orlah applies regardless of whether a tree was planted, extended or grafted. This is the case when someone cuts a branch from a tree and plants it or grafts it to another plant. However, if someone extended the branch of an older tree and planted it in the ground or grafted it to a different tree, leaving that branch attached to its original tree, what grows is exempt from orlah.