Pruning overgrown lilac

[AndrewSmith]

Hi

I'm looking for some advice for trimming an old lilac.

I bought my house last year and it came with a couple of lilacs. One of them (the one I'm talking about here) looks quite healthy, big, green leaves, some (not overwhelming) blooms.

Last year I cut out the dead and crossed branches, but I was thinking maybe this year I should do more. I wouldn't mind if it were a little shorter and bushier at the bottom and with more blooms.

Any suggestions, is it possible to do with this one? It's clearly been left alone for years. What do I do with the large old wood? Cut it down to the ground? And cut the newer stems three quarters up, hoping they will branch out lower?

Or is that hopeless, am I now stuck with this as tall as it is, so just keep it from growing any bigger?

It's on the south side of the house, full sun all day.





Thanks in advance!

[ButterflyLady29]

Cut the larger older branches in the middle of the plant. But if you cut it back now you'll cut off the flower buds. The best time to prune a lilac is just after it finishes flowering. This site should help explain how to prune lilacs:
https://gardening.about.com/od/pruning/a ... Lilacs.htm

[AndrewSmith]

Hm, that website says not to cut down branches till they're 2" thick. I guess that means mine aren't as old as they get? Or do I have a different species, I can't imagine they would get much thicker than that.

Do you think after I get rid of the oldest thickest ones from the middle I can cut the other ones to be shorter? Will they branch out now or is it too late for that?

[rainbowgardener]

Yes, if left alone, the old wood will get a lot thicker.

Conventional wisdom about pruning lilac is to cut one third of the stems off at ground level, oldest stems first. Do that for three years and you have a rejuvenated shrub. But yours is too close to the house. I would focus on cutting down older (but not necessarily oldest) stems that are closest to the house.

Or you can work on getting it out of there and moving it to a better location. After blooming, deadhead all the flowers, then do some root pruning. Take a sharp spade and push it straight down in the ground inside the drip line, cutting the roots at that point. Do this in a circle, all the way around the bush. Your are detaching the roots from the surrounding soil to make a root ball. Then let it sit for a few months. In early fall, dig it out and move it to the new location, where you have already prepared a hole to put it in.

[ButterflyLady29]

The branches can get pretty thick. At diameters of over 2 inches the branches tend to get too heavy to support themselves and they flop over and split. It can happen on smaller branches too. So while the site I linked to recommends not cutting them before they reach the 2 inch diameter they can be cut back when smaller. Just remember that lilacs bloom on older wood, not the new previous summer growth, and the best time to do pruning is right after the blooms start to fade. If you cut it back hard (meaning removing the top portion of the shrub, not just a few old branches) it won't bloom again for 2 or more years.

I agree that it is too close to the house. I would probably take a sprout from near the base of the shrub (making sure to get enough roots with it) and plant that in a better spot. Once assured the sprout survived I would remove the entire old shrub.

Either way, definitely remove the branch that's rubbing against the house, before it comes out of dormancy.

[AndrewSmith]

What about the ones that will be left after I get rid of the oldest ones, do you figure I can cut them to be shorter? Or will the 30% pruning per year eventually accomplish that anyway?

[rainbowgardener]

If you cut down one third each year, in three years all of them will have been cut...

[AndrewSmith]

Right, but in the meantime will the new branches be able to grow well if the older ones are huge and making lots of shade?

[ButterflyLady29]

Yes, the younger and remaining branches will grow and flower better if the older, larger branches are removed.

[AndrewSmith]

Ok, I guess I'll try that, though I'm really worried there won't be enough light. Better than letting it grow even bigger