On Avodah Zarah 53b (before the Mishnah), the Gemara asked and answered (copied from Point by Point Outlines):
5. Question: Only Asheiros served at that time (of the Egel) should be forbidden, but not those served after (Yisrael repented)!
6. Answer: Correct! However, we do not know when they were served, so all must be burned.
Seemingly, if a tree was planted after Yisrael repented from the sin of the Egel it should be permitted! (Some trees are visibly young, or we can count the number of rings.) I did not see anyone address this.
My son, Betzalel Feldman she'Yichyeh, suggested that perhaps we are concerned lest a branch of a forbidden Asheirah (from the time of the Egel) was planted in the ground, and this tree resulted.
Pesach Feldman, Yerushalayim
I also did not see anyone discuss this issue. However, it would seem clear that if a person planted a tree from branches that were clearly not from Asheirah trees (i.e. he brought them with him from Chutz la'Aretz), they would be permitted. If we do not know the origins of the tree, it is possible that the suspicion your son raises is correct.
All the best,
Yaakov Montrose