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Question: My grandmother always warned me not to plant potatoes and tomatoes together or they would cross, then the tomatoes would become poisonous. As a result, since I only have a small vegetable bed, I have always alternated years: a year of tomatoes and a year of potatoes. However, I see people growing them closely together in my community garden and no one seems concerned about poisoning. What gives?
Answer: This is an old garden myth I thought had died out years ago.
Yes, tomatoes (Solanum lycopersicum) and potatoes (Solanum tuberosum) are in the same genus (Solanum) and therefore closely related. However, they won’t cross, at least not under garden conditions (they have been hybridized in a laboratory through a technique called embryo rescue, although the resulting plants turned out to have no garden value).
Tomatoes and potatoes are about as closely related as a lynx and a housecat: enough so that anyone would recognize them as relatives, but not enough for any cross to be possible.
When tomatoes and potatoes are grown close by, bees could indeed carry pollen from the flower of one to the flower of the other, but the pollen would not be able to fertilize the flower, so no cross would take place. And the tomato fruits produced would just be pure tomatoes, as always.
So, no need to alternate plantings: next year, bravely plant tomatoes and potatoes in your garden and enjoy the fruits and tubers without fear of poisoning yourself.