My lilac bush is now a pleasing lollipop shape and has flowered beautifully this year but sadly the flowers are going a bit brown now and I think it's time to give it a haircut. Last year there were no flowers. Was this because the year before I left it late with the deadheading? Do I deadhead now and let new growth come for flowers next year and then tidy it up again later? How much do I trim away with the dead flowers and just once or twice in the year? Hoping to get a white lilac for my back garden now too Many thanks.