If it is growing then yes cut it back. I havent noticed ours getting any more vigourous.

it will only grow as quick as it can it just mite have more shoots is all.

Thank you

I keep cutting ours back and it doesn't seem to get any more vigorous. I think it's one of the plants that you have to keep on top of otherwise it tends to take over. And as we have dogs now we'll have to keep a very careful check on it as it is poisonous to them.

your welcome