Hi, Ms Minna. Some years ago, I read that lilacs need to be refreshed with newer wood on a continuous basis in order to keep blooming. It was recommended that 1/3 of the branches be cut to the ground every year to ensure blooming. This would create a bush with totally new stems every three years.

Check it out. Since you haven't pruned them, this may be the problem.

I think I'll prune them this year then. I never thought to do it because I had lilacs in my childhood home and they were never pruned but were covered in masses of flowers every year like clockwork. We had so many flowers that we'd cut bouquets to give to our teachers (it was my mom's idea).

Here's an article on this. If you google, you'll find plenty more. Don't forget you need to cut the oldest stems to the ground. Also cut out the suckers.

http://www.ces.ncsu.edu/fletcher/staff/rbir/lilac.html

Sorry, forgot: it's possible that your childhood lilac was a more vigorous, common strain, whereas yours are probably grafted. (The suckers can be some common no-good thing with lots of vigor, so cut them off, They will steal strength from the plant.

It's also possible your childhood lilac, if ungrafted, was putting out new shoots every year while the center died, but was still blooming on the younger branches.

Newer, grafted varieties can't be treated like this.

Here in the DC area, we seem to be experiencing no blooming lilacs area wide this year. I don't know if last summer's heat had an effect but it was one of our warmest summers with 90+ temperatures lasting into September.

Some cultivars only bloom well every other year.

They're not cultivars though. Some are seed grown and others are from cuttings. Just your average Syringa vulgaris.

The bloomed every year since they're been big enough except for this year. I think it was the whacky winter, not so much the summer that did it.

I have a small flowered, short lilac that is blooming better than ever though. It's not one of those microleaves... I have to ID it.

I am going to follow advice and cut off suckers and prune.