This past weekend I took care of most of my large potted bamboos by laying them down and covering them with plastic sheeting. (Okay, the plastic is more of a blanket than "pants", but "pants" worked so well in the title and almost made sense, so I left it.) It got too dark to take final photos at that time, but here they are now.
We've had some cold nights since then, with temperatures around 15ºF on a few nights, and the protection seems to be working.
The plants are probably liking it under the plastic. I hope no troublesome critters have found their way under there too.
There's plenty of moisture in there as you can see, and that's exactly what I was hoping for. Probably the biggest problem for cold-hardy bamboo in the winter is cold, dry winds. It's not the cold temperatures that damage the plant (unless it gets much colder than the plant can tolerate), but the winds that dessicate the leaves. Dead, dried leaves don't contribute anything to the plant in the spring, so one key to getting these plants to size up quickly is to help them keep as many green leaves as possible through the winter.
Covering the foliage not only keeps the wind off of the leaves, but it also creates a humid environment. No chance of the leaves drying out in there!
Some of the moisture should dissipate over time, although if I still see wet plastic and green leaves around the end of February I'll be pretty pleased.
There's my whole setup -- greenhouse on the right, and the two piles of horizontal bamboos. The green plants on the very left of the image are the bamboo divisions that I'm experimenting with. One of them is a large potted Phyllostachys bissetii which should do fine in the cold winds -- unless we have a really brutal winter. The others are the Phyllostachys aureosulcata divisions that I heeled in under compost and buried under a thick layer of leaves. They're the plants I'm not too concerned about; I expect them to do fine because they're quite cold-hardy, but if they don't make it I won't be too upset.
The yard looks a lot more dreary than it did a few months ago, but the bamboos sure do add a lot of nice green to my view.
(If you're wondering about the solitary chair in the photo above, I moved it there during the summer. I have plans to build a deck in this area, and I'd often sit on the chair checking out different views and designing the deck in my head.)
So the plastic appears to be doing its job and all of the bamboos are protected. I sure hope I don't need to do as much next year for winter protection... the pile of folded plastic that I need to store in the garage during the warm months is getting pretty large now.
In the spring I'd much rather have the problem of figuring out where to store a large pile of plastic sheeting than the problem of a couple of dozen pots of bamboo with brown leaves and culms though.