Potato + Tomato

Potato and tomato are both members of the Solanaceae family, and that shared lineage creates a serious liability in the garden. Both crops are susceptible to late blight (Phytophthora infestans), early blight (Alternaria solani), and Colorado potato beetle. Planting them adjacent gives these pathogens and pests a continuous host bridge across the bed, which accelerates spread under warm, humid conditions.

The practical guidance is straightforward: keep potato and tomato as far apart as your garden allows, and never plant tomato in a bed that grew potato the previous season (or vice versa). A minimum three-year rotation out of Solanaceae crops is the standard recommendation from most university extension programs. If space is limited and separation is impossible, prioritize clean debris removal at season's end and scout both crops together, since pest pressure on one is a reliable early warning for the other.