When do you trim Leptospermum scoparium and how

I have a small one I bought last year. it flowered for ages, and was so beautiful, I am crossing my fingers this year. It looked dreadful all winter, but has perked up now. As for pruning the advice I've seen says don't. they don't like hard or tip pruning. If yours has got to a size where you want to prune it, then it must be happy! loads of sun, moisture, but not too wet. tricky...