I inherited a 40yr old (?) Lilac boundary hedge with my house it still flowers well but is too tall and too wide with suckers invading everywhere even the lawn. I'd like to keep it if it can be made more manageable/contained. The mother trees are over a foot wide. I tried to 'prune 1/3' of the tallest growth last year and have cut the suckers back quite severely this year, over a foot back towards the original growth but I'm not sure how to go forwad as cutting the suckers just made me aware of how thick the trunks are. It's not really a hedge bit a number of trees surrounded by a miriad of suckers. Is the any way of containing it, it's so established I doubt I could dig it out to start again even if I wanted to. Frankly I'm totally daunted.