I planted 10 American holly trees that were all around 7-8' about 3-4 years ago. They are all doing well (except one and I rerouted the pool hose so it seems to be hanging on). They are all about 10' currently (except the one that was chlorinated). They have not been pruned, except some of the bottom branches to open them up underneath. Since they are in a tree shape right now, I was wondering if I could just cut the tops off each one (about 6 inches) to increase the growth/height/bushiness that I want. I planted them as a screen from a parking lot behind us. I don't necessarily want them bushy, just taller (quicker).
Certified GKH Gardening Expert
Cutting the tops off will make the bushier, but will not make them grow taller faster. The best way to get them to grow taller faster is to encourage them to put energy into growing upwards. In the spring, when you see new growth, trim off all the new growth that is not growing in the direction that you would like. This will focus the plants' energy on the growth that is growing in the right direction. This will produce somewhat leggy growth, but once it reaches the height you would like, you can trim some of the top branches to bring about the bushiness.