(Mishnah) - R. Yishmael: (What constitutes three years to create a chazakah?) 3 months of the first year, 3 months of the second year and 12 months of the middle year, making a total of 18 months.

R. Akiva: 1 month of the first year, 1 month of the third year and 12 months of the middle year, making 14 months.

R. Yishmael: When do I require 18 months? For a grain field, but for an orchard (of various trees), if he gathered his grapes, picked his olives and gathered his figs, it is considered three years.

(Gemara) - Shmuel: These are the opinions of R. Yishmael and R. Akiva, but the Chachamim say that he must harvest wheat, pick olives and pick grapes for three years.

Rav: The Chachamim say that he must complete three full years.