Answer: If the oldest leaves begin to yellow, cut them off the plant. While they may eventually wither away on their own, they are so large and thick that it could take all summer! In the meantime, your plant will look sick. You'll need to dig the tuber in the fall and store it in an area that's cool but remains above freezing. If you keep it in the ground it will freeze solid (even with mulch over the top) and it will also be subjected to excessive water from your rain. As a rule, these plants are pest free, although a hungry slug or snail might attack. Use a snail bait around your plant and you shouldn't have any problems.
Best wishes with your garden!
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