Answer: You will need to leave them outside until late fall after frost but before it turns frigid. Let them slow down and begin to go dormant before you bring them inside. Then store them in a dark cool place that is above freezing but below about 45 degrees. The darkness helps keep them from growing too soon. Water just enough that the soil does not go bone dry. In spring once the weather begins to moderate take them back outside to wake up naturally with the season. Prune them back quite hard in the spring, just as you would a regular Knock Out growing in the ground, but be careful not to damage the graft when you prune. The alternative to winter indoor storage is to do a version of the Minnesota Tip and bury them in a horizontal trench outside, cover that with a generous heap of mulch. Bury them in late fall, dig them up in the spring. Prune them in the fall or spring, or prune partway in fall and finish it in spring so you don't have to dig as big a trench. Good luck with your roses!
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