Kilayim 7:1-2

Kilayim 7:1

If a person bends a vine into the ground with less than three handbreadths of soil over it (around nine inches), he may not plant vegetables there, even if the vine passes through a gourd or a pipe. If the vine passes under a rock, he may plant over it even if there are only three fingerbreadths of soil over it. The bend of a vine (from where soil to till must be left) is measured from where it emerges.

Kilayim 7:2

If one bends three vines into the ground and their roots can be seen, Rabbi Elazar bar Tzadok says that if there are four to eight cubits between them, they combine to constitute a vineyard. If not, they don’t. One may not plant vegetables close to a vine that has withered but if one did, those vegetables would not be prohibited. Rabbi Meir said that the same is true of a cotton plant. Rabbi Elazar bar Tzadok said in Rabbi Meir’s name that this rule also applies to a vine bent into the ground.