Plants still have the same issues with shortening telomeres, but their mechanisms for repairing and maintaining genome stability are much stronger than in mamma

Plants still have the same issues with shortening telomeres, but their mechanisms for repairing and maintaining genome stability are much stronger than in mammals. So if you were to take new growth and graft the same variety of apple tree for the next million years, at some point it would no longer be viable. But how many years that would take isn't really known. On a human scale, yes, they can be considered immortal.