those are lichens.. google it.. totally harmless ...

otherwise.. it might be a lilac leaf... but i cant be sure in the first pic ... maybe lilac seed pod at top right ...

you should see a post here.. about my lilac going wild this year.. do they look vaguely familiar???

based on these pix.. i can not tell what the problem is.. but surely food/fert will not help ...

i might be tempted to cut it down to about 4 inches.. and see if it can rejuvenate itself ... if it is in fact a lilac ....

ken

ok I just checked the "lilac gone wild" post and yes they do look similar. The blooms were also similar, just a more lighter purple. I live in upstate NY so the blooms were beautiful for about a week, before they started to fade in color and then were gone.
Anyway, if the lichens are harmless, then I guess I wont do anything about it. I was thinking of scraping them off, lets see and maybe pruning the plant a little.

google renovation pruning of flowering shrubs...

you would basically cut 3 of the large stems to about 3 inches.. and watch them regenerate from the ground up.. next year after flowering... remove the rest ...

you could have a very nice plant there.. if you do it right...

ken

Hmmmmm....I'd have to say that that is not a very robust lilac specimen :-) They do tend to grow a bit leggy and somewhat sparse with foliage but that one looks exceptionally weak - lots of dead wood apparent and not all that much leaf growth. I wonder if there may be something else going on with it, like planting issues initially. How much sun does it get?

And while the lichens are harmless, they DO tend to readily colonize plants that have other issues or what is commonly known as being non-thrifty :-)

When only moved into the house about 9 months ago, but from what I can tell, it does get full morning sun and shade in the late afternoon. Right now, it has really less foliage and lots of thin branches. I will go ahead and prune it and then see how it does through the season.

I see some splitting of the woody stems, too. A very bad sign. It might be worth cutting this shrub all the way to the ground and hoping for the best, as Ken suggests. It's not the best time to do this, by any means, but at this point I don't see how the plant could fare much worse. :-(

here in my z5.. the lilacs are just finishing bloom..

it is the ONLY time to cut them down ... if you have any dream of flower next season ...

if you dont care about bloom.. cut them any time ...

but.. when it all boils down ... its improperly planted ... too close to the deck.. get rid of it ... link below to what lilacs can do, when healthy .... basically swallow that deck

cut it back to about 3 foot spikes.. and just start digging about 2 feet out from the stump .. using the spikes to wiggle and find the major roots.. couple hours of good exercise.. and you will be all set ...

its simply not worth the effort to rejuvenate a mis-planted plant ...

ken

Here is a link that might be useful: link