trimming lilacs

[Tom7227]

We have three old lilac bushes in the yard and they are about 15 feet tall. I need to cut them back but I don't know how far I can go. I am fairly sure that you are supposed to wait until the bloom is over. I took out two pieces that were about as thick as my wrist but there are maybe 20 or so that are pretty spindly and tall. I would like to cut them down to maybe a few feet and force all new growth but I wonder if that's too drastic.

Thanks for your time.

Tom

[lawnbuilder]

If you cut about 1/3 of the oldest growth out every year it will continually be rejuvenated. However if you wish to go more severe I have cut everything to about 6". Doing a dramatic trimming will often cost you flowers next spring since yes trim right after blooming is the correct method. If you want them shorter I would trim to about the size you want and trim out about 1/3 this year then get on a maintenance routine of light trimming with takin out some of the oldest growth yearly.

[delcecchi]

You can whack them off to knee high. They will grow back. Then you can thin and prune to the height and shape you prefer.