3,060. Whose Actions (or Inactions) Sanctify Mixed Produce of a Vineyard?

Hilchos Kilayim 5:8

The prohibition against mixed species of a vineyard applies both to one who plants them and to one who finds mixed species in his vineyard and leaves them alone; in both cases the produce is sanctified. Since one can’t consecrate something that isn’t his own property, if person A drapes his own vine over person B’s grain, he renders the vine consecrated but not the grain. Similarly, if he drapes person B’s vine over his own grain, he renders the grain consecrated but not the vine. If he drapes person B’s vine over person B’s grain [or person C’s], he doesn’t render either of them consecrated. This is why, if someone plants mixed species in his vineyard during shemittah (the Sabbatical year), he doesn’t render it consecrated (because Sabbatical-year produce is ownerless).

Hilchos Kilayim 5:9

If someone sees mixed species growing in another person’s vineyard and allows them to remain, that person may not derive benefit from them, but everyone else may. If the owner of the vineyard allows the mixed species to remain, they become consecrated, and therefore prohibited to everyone, as we have already discussed.