How tall do you want your hedge? These can easily grow to 10 feet. I had a neighbor I wished to hide and grew them that tall. If you do that they get little light at the bottom and show their legs which are not that attractive. Al

I would like them to be at a 5ft height but would like them to be dense and not leggy.
I read somewhere pittosporum need to be pruned early and hard so wasnt sure when to prune to get desired effect.

Thanks

If you don't want the legs to show it is important that you keep the top more narrow than the bottom so you get light down low on the plants to stimulate low growth. Al

In my experience, you can hack them at any time and they will recover. Better if you don't let them get out of hand as I did. Also, if you get one that is a seeder you should dispatch it immediately!