I would imagine yes. You may need to thin out that remaining bottom, or cut near the ground, though. If nobody here knows try the shrub forum. I am not an expert gardener, just posting what I think will help.

Thank you Poaky, I'm glad to hear that because it looks a little bare. My lilac isn't a shrub though, it's a tree! It has a trunk, which is why I posted it here.

giving a lilac a haircut is not the way to go ...

search out: rejuvenation pruning of flowering shrubs... you are supposed to remove 1/3 of the branches... at ground level ...

whats going to happen.. is that it will now grow again... the same height it was before.. but on top of what you left.. eventually collapsing due to such.. in years i mean ...

ken

ps: your words are a pit confusing.. w/o a pic.. is this the standard shrub ... or a lilac on a standard .. on a trunk ???? ... obviously... you wouldnt do rejuvenation on a standard ...

Any chance you are talking about a Japanese Tree Lilac? (Syringa reticulata 'Ivory silk') I have one and it is a beautiful tree. They really do get surprisingly big. I would just wait a growing season and see if it fills out at all in the bare areas. It's a shame it was planted so close to the house. They need a lot of room.

This is a lilac tree not a shrub. It has a trunk! Syringa Vulgaris. I pruned it one third way down from the top (after it finished blooming). Ken are you saying I should have pruned it lower? One - third up from ground level? If I did that, there wouldn't be any branches left on the tree, maybe I didn't understood you right. I've pruned it before and it has never collapsed. It has always grown new branches. I just wanted to know if the leaves will come back this summer?

Syringa vulgaris is a large deciduous shrub or multi-stemmed small tree. We generally refer to them as shrubs in these parts, but whatever one wants to call them is fine with me. Mention "syringa vulgaris" and it's pretty well known what you've got.

The rejuvenation practice is to take out 1/3 of the trunks, not 1/3 of just the branches or branch tips a third of the way down. Say you have a mature specimen with 9 trunks, take out 3 of the oldest so new ones can grow in to take their place.

I get this done by an arborist every 10-15 years. This winter resulted in some breakage on the older trunks; not as much as I feared would happen, mercifully. But, after they bloom, they'll get the rejuvenation and clean up they need.

Sorry, I was imagining a shrub with a bunch of small leafless lower branches near the ground.