Uktzin 2:9-10

Uktzin 2:9

If a cucumber was planted in a pot until it grew beyond the pot, it is ritually clean. Rabbi Shimon asked why this should be. Rather, he said, that part that was already susceptible to ritual impurity remains that way, while the part that's ritually clean can be eaten.

Uktzin 2:10

Vessels of cattle dung or of unfired clay through which roots can pass don’t render the seeds planted in them susceptible to ritual impurity. A perforated pot doesn’t render seeds susceptible to impurity but one without a hole does. The hole must be one through which a small root can pass. If the pot was filled to the brim with soil, it is treated as a board without a rim (i.e., without a receptacle and insusceptible to impurity).