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Hi, I've had tons ofHi, I've had tons of experience growing potatoes, and my advice is to hill up to about 18 inches; sounds like you ought to be about there if you've been hilling all along. By the time I've hit 18inches, I've always run out of any more soil to hill anymore! Harvest when the tops of the plants die. My plants usually get to be about 3feet tall before they start to die. Good luck!

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