I rarely disagree with Mike but fertilizing is not the answer, especially heavy fertilizing. Lilacs rarely require it and in fact fertilizing when not required can lead to lack of flowering or minimal flower production. Can you explain what you mean by "severe pruning"? Rejuvenation pruning of old, established and declining stands of lilacs are one way to bring them back to life but there is a correct way to do so. Do the lilacs sucker? Transplanting suckers can also regenerate older plantings.

I had always heard that the way to rejuvenate old lilacs is to cut to the ground one-third of their branches. But not just any of the branches - the OLDEST branches. The thickest, woodiest, most tree-trunk-like branches. To the ground.

The theory was that it allows more light and nutrients to reach the younger, more vigorous branches to prolong the life of the shrub.

Is this still a favored method of rejuvenation?

^^^ Yes. But you only start with the oldest :-) By the end of year 3, you will have removed all the old growth.

The pruning has consisted of cutting the shrubs back to the ground every 10-15 years. I was not involved in those events, but there were always lush blossoms within a year or so. My brother says the poor performance has just been in the last few years. The last pruning was 4-5 years ago, I think.

I went out just now to take some pictures. I’m realising that there are large trees that were planted over the years that are now causing significant shade where the lilacs are located. Maybe we need to move them. When is a good time to take lilac cuttings? Or can you?

Lilacs sucker, often heavily. And a sucker is like an already rooted cutting so very easy to dig up and transplant elsewhere. I'd start with suckers first, then try cuttings taken in early summer from vigorous new growth......if you can find any. Older growth will not take easily.

I will look for suckers. However, the tree growth is close enough to the lilacs that I think I will run into heavy roots.

Lilacs often do not age gracefully. Alot of branches will die and it tries to compensate by sprouting new "bushes" around the base of the old one.

>"I have moved in with my mother" ___ Martha, what is the ownership status of your own farm?

Four,

Sorry for the delayed response. My farm is up for sale as a result of nasty a nasty divorce.