January 23, 2011
     Brrr...Dang it has been cold so far this year... going back to early December we have experienced below normal temperatures nearly everyday with very few days when the temperature reached 0C. There have been 4 nights thus far where the low temperature was been between -16C & -18.5C. Fortunately we have not had any lengthy periods of high winds, only a few days here & there. These conditions offer a great observation opportunity regarding how the different species of bamboo handle temperatures at -18C.  As a reminder, most resources that list bamboo hardiness in terms of temperature use the standard that 'the listed temp is the point at which leaf damage begins to occur. I continue to challenge these ratings as I find that most bamboo will show leaf damage at temperatures well above the listed one and in my experience those temperature ratings more closely approximate the point at which the bamboo will die back to the ground. There are of course, some exceptions.
       Below I have included photos of different species that are exhibiting different degrees of cold damage, ranging from none to likely top kill. All of these photos were taken after a winter low of -18.5C with the qualifier that my property is very hilly and wooded which results in some temperature variation from planting site to planting site. My thermometer is attached to a deck post in the shade about 2 meters from the house. Regardless of how your bamboo looks there is really nothing you can do at this time to help them recover from damage they've already sustained. About all we can do would be to try to prevent additional damage to prized plantings by covering them during the next cold snap.
     If your bamboo has burned leaves and you are concerned about the health of your bamboo, I would suggest that you examine the dormant leaf buds.  These are the scaly looking things on the branchlets. Sometimes they will have started to elongate during a warm up and they will be easier to review for damage.  Close examination may reveal that the buds are still firm and green in which case they will likely be viable.   If they are easily flicked off or appear to have poor coloration they may well be dead.   In any case don't do anything now, wait until late spring to see if they produce new leaves.   Dead culms will become apparent in time as they fade to blonde/tan and these may be culled when obviously dead but they can be helpful in protecting new shoots so you may wish to wait until after the new spring culms are leafing out before you cut the old culms out.