I have five Black Bamboo plants spaced out in an (approx. ) 3 feet wide by 18 feet long (4feet in depth) container. The tallest culms are about 12 feet now. Someone told me that the bamboo should be fertilized in Sept. or Oct. with a high nitrogen grass fertilizer and again mid-March. Also that I should mulch with mushroom manure over winter. Is this correct information? If so - how much fertilizer and manure should I use. I am hopeful that the bamboo will get taller next year and fill out to make a good screen against the neighbours' tall house.