Halakhah sur Orlah 1:2

From the laws of the commandment is that which they, may their memory be blessed, said (Mishnah Orlah 1:1) that one who plants for a hedge or for beams is exempted from orlah, as it is written, "food tree" - meaning to say that he did not plant it with the intention to eat its fruits, but rather that the tree will be a hedge around his garden, or with the intention that he will make beams for his house with it. [If] he planted it for a hedge or for a beam and went back and thought about it that it should be for food, he is obligated in orlah - once he mixed a thought of obligation into it, he is obligated. And what protects the fruit is [also] obligated in orlah; and like they expounded (Berakhot 36b), "'Its fruit (et piryo," the word et not being essential to the meaning), [to include] that which is secondary to the fruit" - meaning to say that which protects it. And it is with certain conditions known to our Rabbis, may their memory be blessed, that that which protects the fruit is forbidden, until the time that the fruit reaches the category of the prohibition of orlah. And also that the fruit needs it so much that if you took that which protects it, the fruit would die. And therefore, they, may their memory be blessed, said that only the berries of the caper tree are obligated in orlah, but the capers (themselves, which covers the berries) are permitted, from this reason that we said; as it is well-known that if you take the capers before the fruits reach the prohibition of orlah, the fruit does not die. And the law of what is planted for the many (Mishnah Orlah 1:2), one who plants for a commandment and one who plants in a holed pot that he is obligated in orlah; and the law of a young plant that is enmeshed in an old plant (Nedarim 57b). And the rest of its laws are elucidated in Tractate Orlah.