Q.I Have An Old Lilac Bush That Was Never Trimmed. It Was About 20 Feet Tall. I Cut The Bush Down To About 10 Feet High. I Read That
I should cut the bust to about one foot from the ground. Should I recut the bush down to a foot or keep it where it is now? I lov e this bush and I don’t want it to grow back in a bad way.

Certified GKH Gardening Expert
What you have done is, usually, appropriate. If the shrub is stubborn, and it does not come back, then it may be necessary to cut down to about 6 inches from the ground.
This is going to keep the shrub from flowering for about 3 years or so. It will help it to be more shapely and robust, however.
Here is an article for more information: