It is around 3 weeks into winter and the lowest temperature so far in my garden is 5.8F, nothing close to being a threat to most of the bamboos that are rated among the hardiest. We are in zone 6a so temperatures can get a little bit below 0F, but so far we have hardly had any snow and there is not that much arctic air built up in the northern hemisphere for this time of the year so I really doubt my bamboos would have any problems even if they were unprotected. Most of my bamboos will start leaf burning anywhere from +5F to -8F, and they are nowhere near mature so their hardiness should continue to increase for the next few years.
Here's Atrovaginata. I decided to tighten the wrap because it was loose and could be blown off.
Here's the yellow groove(phyllostachys atrovaginata)
Phyllostachys Parvifolia: Still no signs of damage on any of the bamboos, but the protection is there just to be safe.
I also added a layer of compost which is not that high in nitrogen however it has been worked through by worms for a long time so there are many micro-nutrients that can help benefit these boos. Once I take off the tarps in March, I can spread it out a little bit better to give the plants a little boost for this year's shooting season.
This picture sums up how the weather has been so far this winter. Aside from 1 very cold night in the single digits, temperatures have been well above average for the last 2-3 months, and will probably stay that way through the rest of winter.