Answer: According ot your zip code, you are gardening in USDA winter hardiness zone 6A or the coldest part of zone 6. Depending on your microclimate, it may be as cold as zone 5. Unfortunately, this particular bamboo Bambusa multiplex `Alphonse Karr` is only considered winter hardy into zone 8. It would not be expected to overwinter successfully outdoors in your area, so I think it is most likey dead. If you think there is a chance they are alive, be patient and see if they leaf out or send up new shoots from below ground. I'm sorry about your bamboo.
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