Answer: These are tropical plants and should be brought inside before the temperatures drop below 50 degrees. If exposed to too much cold, the tuber will rot and the plant will die.
To some extent the amount you have to cut off will depend on how confusedly they have twined and how much patience you have to untwine them and also on how much room you have to keep them indoors.
In order to grow well indoors these sunlovers need the maximum possible amount of sunlight -- these are tropical plants after all. In lesser amounts of light they will languish but survive; in lower light they will do better with lower temperatures (say in the 50's or 60's) which help them to slow down naturally rather than keep on trying to grow full tilt and becoming leggy as a result. If they do become leggy or lose their foliage, simply trim them back a bit next spring when they begin to grow again.
To prepare them for coming indoors check them carefully for pests ahead of time. Also, over several weeks move them gradually into a partly shady location to acclimate them to the lower light levels indoors. As they slow down with the shorter days, reduce water and fertilizer to compensate for the reduced growth.
Next spring, follow the process in reverse to avoid "sunburning" them and adjust your watering and fertilizing as they make their spring growth again. Good luck!
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