From: Rabbi Moshe Sofer
To: Rabbi Nachum Trebitsch
A Jew who leased an estate was obligated to plant new trees annually, creating inevitable orlah concerns. The Chasam Sofer ruled that trees bearing fully ripened, normal-quality fruit carry a presumption of permissibility and need not be suspected as orlah, especially since doubtful orlah outside Eretz Yisrael is permitted; however, trees bearing visibly thin, underdeveloped fruit present a near-certain orlah concern and may not be eaten. The lessee is not obligated to actively search for orlah fruits, and the final practical ruling was deferred to Rabbi Trebitsch.
Source: Shu"t Chasam Sofer YD §286