JuliaLilac
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Location: Montreal, Quebec, Canada - Zone 5

Rejuvenating a lilac

Hi there,

I live in Montreal, Canada and have a large, neglected lilac tree just outside our back window. It had begun to get quite leggy and tall, with blooms only on the topmost branches (which I can see through my bedroom window on the second floor).

I decided to use the 1/3 method, and have been cutting down some of the oldest branches for a couple of years now. My question is this:

How much of the new growth should I be cutting? There are quite a few new branches in the middle of the tree that are very leafy (no blooms yet). Should I be thinning them? How many should I be leaving?

Thanks for any information or suggestions you may have!

tomc
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Re: Rejuvenating a lilac

If your lilac gets full sun, it will give more blooms in the spring. You could perhaps give it some lime too.
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HoneyBerry
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Re: Rejuvenating a lilac

I have lilacs. They get lanky if there are other trees or shrubs close to them. For example, I planted some lilac sprouts in a temporary spot next to some arborvitaes. Their growth was very long and lanky because they were trying to reach beyond the arborvitaes. The blooms are on the top part of the tree. My other lilac plants are bushier. I do prune away branches that are in the way or to shape the trees. Other than that, I don't prune them.
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PaulF
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Re: Rejuvenating a lilac

We had the same problem several years ago with lilacs that were probably fifty years old and had never been pruned. You are correct in pruning out about 1/3 of the clump making sure what you prune is the oldest wood. Be sure what you prune looks like a tree branch, the roughest looking rather than smooth wood. Many say two inch sized stems should be pruned out. We also trimmed out the skinny suckers at the base of the shrub.

After flowering is done for the season you can shape the lilacs. Ours were maybe fifteen feet tall and we shortened the leggy branches and generally rounded the entire shrub to the shape and size we wanted. It is difficult to prune too much, but that will not really hurt the plant.

The next year there were blooms but not really a big amount. The next year we pruned a few more of the old, woody branches but not a third, maybe just two or three branches. And we did not shape the lilac that year. Then by the second year after thinning , shaping and pruning, the blooms were larger, lasted longer and the numbers were way up. Since then some nominal pruning to keep the shape was all that was needed. Always wait until the blooms are gone before pruning branches. Buds for next year will form very soon after the flowers fade so if you wait too long you will be cutting off next years blooms.
Paul F

JuliaLilac
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Joined: Mon May 30, 2016 4:47 pm
Location: Montreal, Quebec, Canada - Zone 5

Re: Rejuvenating a lilac

Thank you all for your replies!

Paul, I was just wondering how much of the new growth I should be thinning out. There are quite a few shoots coming up from the center of the tree, and I wanted to make sure it wasn't too crowded in there. I was happy to see one bloom on a newer stem in the center! I'm cutting the old branches down to the ground because they are so skinny and bare with bushy tops. I think once I remove all the old branches, the sun will be able to get to the center and there will be more blooms on the newer wood.

It takes soooooooooo much patience!

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rainbowgardener
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Re: Rejuvenating a lilac

Where I used to live, we had a huge old lilac. I never did as much pruning on it as I should have, just deadheading it was a big job. You do know you need to clip off spent flowers before they set seed? If you let it set seed, it won't flower as much the next year.

Anyway, one thing I did do was prune out most of the cross branches that were growing in towards the center and some of the new stems that were coming up right in the center as well as old wood, just to open up the center and let more light and air in. It seemed to respond well to this.
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tomc
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Re: Rejuvenating a lilac

Many were the old guys in NH, VT, ME over the years that "chainsaw" pruned their lilac by cutting everything off about knee high. Every seven to ten years. I like what your doing better.
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