Bamboo clumping

About 2 years ago I bought some bamboo from Homebase - can't remember the exact species but could find out - to provide some cover where my garden is overlooked.

I know I researched the species, and accepted all the warnings about it clumping as it is in a bed, and I'm happy for it to clump.

However.....it's not growing upwards as much as it's clumping.
When I bought it, it was about 1.5m. After year one it got to just above the height of the fence, say 2m, but doesn't seem to want to grow higher - just clump sideways. Is there anything I can actively do to encourage it higher? I have tried shouting, cajoling gently, and playing a tin whistle, to no avail. I did get lots of worms though.

tl;dr - How can I get my bamboo to grow upwards?