3 years ago we planted a new hedge of cottoneaster shrubs. They are growing well for the most part, (I had 2 different kinds, one is doing very well, the second is somewhat stunted). The one with shiny leaves and black berries is doing very well. The other one has smaller leaves of a lighter, not shiny leaf and no berries as of yet, it seems to keep dying back and restarting its growth each spring. I think I will probably replace these ones next year. I am wondering how and when to prune the other kind to create a formal hedge. Right now they are apprximatly 3' tall. They dont seem to be filling in the space between each plant well but are growing thicker and taller each year. Should I trim these back severly to promote a wider spread of growth?