By Bamboo81
United Kingdom 
It have three unknown types of bamboo (inherited from the house I've just moved into) All seem to be cut to a 5ft height but after a lovely summer and some additional care they are now sprouting much taller canes. They look unsightly now, but if the rest of the plant were to grow to this height I'd keep them. I've read somewhere once a plant has been lopped it never grows any taller ? so either this is bucking the trend or, perhaps I should read this,only those canes which have been cut never grow taller.
Might this be bamboo flowering?
Interested to hear views on what to do (before my husband takes direct action himself! The attach photo is of a black bamboo clumb.
9 Jul, 2015
If that's black bamboo (phyllostachys nigra), they do this every year - throw up long, sappy growths. Ultimate height of this plant is around 13 feet, which is probably more or less the height of the new growth. You can leave it in place, or cut it down to a more reasonable height, whatever suits.
9 Jul, 2015