HELP! Lilac bush needs massive contaiment/health help!

My elderly mother has let her lilac bush sprawl and grow for years and years. She loves the blooms and wouldn't let anyone trim the bush for fear it wouldn't bloom the next year. However, the bush is now totally out of control, sickly and not blooming well at all -- it is time for a massive containment attack and some equally aggressive moves to make it healthy again.

I think, at 75, she fears if we cut it back too much she'll never see it bloom again but, frankly, it is dying as it is now. The dirt it is in is neglected and depleted of any nutrients. (It is the most depressing gray dust I have ever seen.) The blossoms hang on teeny little branches and often fail to open. There is lots of dead wood and a million little runner/sprouts under it. It is over the top of her front enclosed porch (which makes it about 10' tall and 8' wide) and I would like to cut it down below the windows which means I'd be topping off at least 1/2 of the bush's height.

What is the proper way to get a lilac under control? What sort of damage will I actually do to it if I cut it way back? How long is a reasonable period of time for it to heal and start flowering again if we add some good, nutritious soil and maintain a healthy environment for it?

Thanks for the help.

That's really too bad. Reading on other forumns, lilac blooms grow on NEW wood. So, since lilacs are in bloom around now you should cut the branches within the next couple of weeks. Also, they don't like nitrogen fertilizer, so fertilizing the grass nearby might be hurting bloom production. Of course, they like sun, so look around at what might be keeping the sun off their faces. It may take a year or so for the blooms to come back if you cut it severly...maybe you should consider taking about a third of it off (plus the dead wood) this year and see what happens next year.

This was a good bit of information:
http://www.thriftyfun.com/tf001370.tip.html

Try to get Mom to undestand that doing nothing will most certainly cause it's demise. GOOD LUCK!

Also there's this excellent article:
http://davesgarden.com/guides/articles/view/928/

And today's article on pruning forsythia might help you understand about pruning flowering shrubs in general:
http://davesgarden.com/guides/articles/view/2480/

Taking a 1/3 off and general clean up will make a big difference in looks and health - so maybe approach it that way as drumlin said..... slowly - instead of one big major effort. A third each year maybe. Also is there another area where you can plant a lilac ? While this one is being tended/rejuvenated ... your mom can see and smell the other!

When Is the best time to trim the Brush It has bloomed and now the flowers are going should I trim after the flowers have all turned or should I wait for fall to trim it
Dimmer

Do it now. Almost every perennial fairs best when its trimmed right after the blooms are gone. If you trim in the fall you'll be trimming off all the blooms for next year!

Thanks so much I will trim after they all turn brown right

Yep, you don't really need to wait until they are brown; if the flowers are done, they're done. Give it a good haircut, cutting about 1/4 inch from a new little shoot bud (pay some attention to where you're cutting on the branch). I made an effort to do that with my perennials last year, and this year they look just great!

Do new little shoot buds appear on old wood? My mother's lilac REALLY needs to be taken under control and 1/3 of it needs to go away -- as well as the dead wood inside it.

I always think of new shoot buds as being on the very ends of a branch and those branches, very soon, be in a compost pile in the back yard.

Nope, when you cut the branches some of the shoots will certainly, um, shoot out of the little nubby nothings that they are today. Rule of thumb is to cut even into some of the green wood, so down (from the top) to 1/4 inch above first green nubby thing, assuming you want to keep that much of the branch. Cut even lower if you want to get down to a good thick stem. Some shoots will come out of the ground from the roots. And, some branches will simply die. If a lilac is really out of control, you might want to consider cutting about 1/3 this year, and see how it goes. Then next year pay attention to which branches aren't doing so well or need shaping, and cut about 1/3 again. Don't be afraid to just cut dead branches out. It's not going to look great the first year after you cut back, but be patient. I was kind of tentative with my azelea for a couple of years, and then last year after the flowers were gone I cut about 1/2 back and really took some of the branches all the way to the ground. Some branches died, but the ones that lived REALLY sent out the flowers!