A few years ago we planted 20meters of clumping bamboo trees along our pool to give us privacy from our neighbour who's backyard veranda overlooks our backyard. The bamboo looks great however they drop a lot of leaves (something we did not know at the time of planting and after consultation with a horticulturalist). Is there any other tree or large bush that we could replace these with that grows around 4 - 6 meters and doesn't drop leaves or flowers?