Answer: Tomato and potato plants are both members of the nightshade family so their leaves and their blossoms appear similar. But, the potato plant produces fruit in the form of tubers underground and the tomato plant produces fruit on the top of the plant. The round, green tomato-looking things on the tops of your potato plants are seed pods. They will grow to about one-inch in diameter but they will never turn red and they are not edible. The blossoms on potato plants simply indicate that tubers are beginning to grow underground. Leave the seedpods alone and harvest your potatoes after the foliage dies down.
Hope this clears up the mystery for you!
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