Hilchos Maaser Sheini and Neta Revai 10:1

Neta revai applies to everything to which orlah applies; if something is exempt from orlah, it is likewise exempt from neta revai. This is derived from Leviticus 19:23-24: “For three years it will be orlah... and in the fourth year....”

Hilchos Maaser Sheini and Neta Revai 10:2

If someone plants a fruit tree to serve as a barrier for his garden, or for its wood rather than its fruit, it is exempt from orlah. Let’s say that he planted it to be a barrier and then changed his mind and decided to use its fruit, or he planted it for its fruit and then changed his mind and decided to use it as a barrier. In either case, since there was an obligating intention, it is liable in orlah. If he planted it to serve as a barrier for three years and then to use its fruit, it is exempt from neta revai. This is because when orlah doesn’t apply, neither does neta revai.