What is a Tree?

 https://www.yeshiva.co/midrash/6863

 The Chazon Ish (Orlah 12:3) is dissatisfied with both of these approaches because there is no source in Chazal for this definition of a tree. However, he agrees that eggplants are not prohibited because of orlah for a very different reason. He contends that orlah can only ban the produce of a tree for its first three years but cannot ban the species completely. Therefore, a species that produces fruit for no more than three years cannot be a tree whose fruit is orlah. Instead, we must conclude that this plant is not a tree and therefore its fruit is not orlah.