Pruning an overgrown lilac tree

[PinkCamelias]

My lilac tree is very leggy and top heavy. It doesn’t flower much. Last year, after flowering, I had it lightly pruned. It’s grown even taller since then (it’s ca. 3,5 m now) but there is no new growth at the bottom. What should I do? I know that it can be hard pruned over three years, but shall I do it even if it only has a few thick trunks-branches? It would mean cutting 1-2 a year and it might look a bit strange in the meantime. Also is it certain it would regrow? A branch that overlapped with a rose arch was removed and nothing new grew from the spot it was cut. Any advice?

Mine's in flower right now and I've pruned it over the years. It's bushy from the base but far too tall.

How to Prune Lilacs: 9 Steps (with Pictures) - wikiHow
When and How to Prune Lilacs Like a Pro
How to Prune Lilac Tree: Expert Tips for Healthy Growth - Evergreen Seeds

For some reason, they don’t flower the following year where there has been a cut. Personal observation so it might not be true for all varieties.
So you prune heavily this year and hope for flowers the year after next, with the associated growth in the meantime. Or you replace it with a shrub variety.

They'll not flower the year after a hard pruning. I'm going to hard prune mine but I'm not concerned about killing it.

I gave mine a careful pruning last year and it's looking great this year. I don't like it enough to justify the space it takes.

Thank you for your replies! All the advice I read is about multi-stemmed bushes. I had these in my previous garden and pruned with no issue. Here, however, I have only a few very thick and woody branches/trunks. Prunning them at the base would mean removing one a year, but that would reult in effectively removing a third of a canopy. Pruning them as they fork out higher would mean perhaps removing a bit less, but the new growth would start quite high up, if i understand correctly. Basically, I am unsure how to proceed with a tree like that one.

I could replace it but I would rather not, if possible, because it is big and it would be quite some work.

I'd cut it on one of the red lines.

but I'd be prepared to lose it.

There will be a lot of mess but you could get most of it shredded.

Thank you @StationJack !

You're welcome. I prune fruit trees too. It's easier to keep them small. The apple trees are short enough for me to be able to pick the fruit without having to stand on anything and produce a hefty crop.

There is something nice about lilac but my garden isn't big.

You could bite the bullet and prune even lower but accept it won't flower for a few years. A high potash feed such as tomato feed or sulphate of potash will encourage flowering.

I'd recommend not hoping for flowers for about 4 years.

Ok, I’ll be prepared for no flowers then! I love lilacs so it may be worth it; as it is it flowers very little. There’s a new one growing behind it, purple, it must have grown off the roots of an old tree I didn’t even know had been there. Maybe this one will fill the gap for some time, if it be one’s an actual shrub.

Is this hard pruning done in winter?

You'll probably get some after 2 years, but it will take time for the tree to have much growth for there to be flowers on.
They're quite tough trees and last a long time. Mine's about 30 years old.

My irises are out.