Each cane only grows vertically for one year, so you'll have to wait for next year's canes to appear and grow to their full height before you see any extra privacy. Make sure they get plenty of water
Bamboo canes usually grow during a six week period starting in May in the UK. They remain the same height and circumference thereafter. Once this growth period is over, l remove all the short and spindly canes each year, leaving only the ones that are the most robust and best size and colour. You can give your plants a boost by applying a few handfuls of blood fish and bone around the base of the canes in late February. The nutrients will then become available by the start of the new growth period. By pruning your bamboo selectively each year you’ll encourage wider and higher canes in future years. Be vigilant though and cut down any canes emerging where you or your neighbour don’t want them immediately!
Be very careful what you wish for. It will not be long before you and your neighbour on the other side of the fence will be getting out your machetes to clear a path through the bamboo. Even polite bamboos become thugs ard take over any spare ground they find very quickly. Then it is extremely difficult to get rid of them.
Mine grows in similar confinement, plus with a sandstone seam not far below. This has encouraged good behaviour..............so far! Enjoy your bamboo, keep a close eye on it, remove all unwanted canes as they appear and it will be fine in that situation.
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Make sure they get plenty of water
Really excited about seeing the new canes emerging next year.
Then it is extremely difficult to get rid of them.