To all those knowledgable on this topic:

I cannot convince contractors I am working with on the importance of separating valves/stations to meet various plants water requirements. I am asking that all trees on the property be on one line, all shrubs on the property be on one line and all perennials/annuals on the property be on one line. The systems are all drip and not standard surface irrigation. Do you agree with this setup? Doesnt our background of proper horticultural practices support this setup? If so, what kind of literature can I get a hold of to back up this claim??? Any info will be much appreciated!