Answer: This bamboo is considered winter hardy to USDA winter hardiness zone 7; unfortunately your zip code places you in zone 6A or the coldest part of zone 6. This means your bamboo would not survive the winter outdoors even if it were planted in the ground with optimum insulation for the roots. In containers, with even less insulation for the roots, I really would not expect them to survive your winter outdoors.
You might be able to protect them by bringing them into a garage or cool basement where they can be kept above freezing but quite cold, say a maximum of 45 degrees. If height is a space issue, they could be set horizontally. This way they could rest for the winter and then be brought outdoors again in the spring. Keep the soil just barely damp, not bone dry, while they are in storage. Keep them outside until they have stopped growing for the season in late fall. Take them back out in early spring so they can wake up naturally with the season. Good luck overwintering your bamboo!
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