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How to Prune Lilacs correctly!

How to Prune Lilacs correctly addresses the different reasons to prune. Each may have it’s own method.

Many complain that their large lilac is not blooming and there can be many reasons why, which I talk about in this post Lilac Not Blooming?

One reason can be that your lilac has not been pruned well or correctly.

Let’s start with the reasons to prune.

heirloom lavender lilac bush in full bloom, Flower Patch Farmhouse

the Lilac has been neglected for years

Common Lilacs can last for decades but they bloom best on wood that is under 5 to 6 years old. They will bloom less and less on wood that is older. Plus the blooms are usually too high to enjoy once that old.

For older lilacs that have not enjoyed good annual maintenance a more severe renovation prune is in order.

A good time to do this is in early Spring before new growth begins. Check to see if your lilac has been grafted. Check the main trunk of the Lilac and see if there is a bump and difference in bark. That would be the graft union.

Grafting is where you join a scion of one cultivar to the root stock of another. If you discover it is a grafted Lilac be sure to remove all suckers from around the base.

The shoots or suckers coming up around the base of grafted Lilacs will not be the same bloom type.

Never cut below the graft joint. If the lilac is not grafted you can cut the entire plant off at the ground but don’t expect any blooms for a couple years.

Pruning to the ground is the most drastic method but it does work.

Less intense renovation prune

You can also do a renovation prune over a 3 year period. When pruning this way cut out any dead or weak canes, then cut out 2/3rds of the suckers or shoots coming up at the base, leave 1/3 for future blooming stems. 

How to Propagate Lilacs from Suckers, easy enough if you have a sharp shovel and a bit of muscle.

You can actually dig the suckers up and pot them to make more lilacs if you wish, they actually mature faster than taking cuttings and rooting them. 

Cut back 1/3 of the older lilac canes or branches. The following year cut out the next 1/3 of the oldest branches then the final year cut back the last of the oldest branches.

Doing this in 1/3’s will let you have blooms and still cut back the old worn out branches fully renovating the lilac.

Some say to have only about 10 canes per bush for best health and others say 2 or 3. The lilacs I have cared for have between 5 and 10 canes and bloom beautifully.

Annual pruning

Cutting Lilac blooms to bring into the house is a great way to keep your plant healthy. Make the cut at the base of the flowers. This is similar to deadheading but you are cutting off the flowers before they are dead.

The beauty of cutting the flowers is you keep spent blooms from sucking energy from the rest of the lilac. And you get to enjoy their sweet perfume in your home.

Deadheading should be done as soon as possible after the flowers fade if you haven’t already cut them to bring into the house. The old flower cluster should be cut off at its base, just above the two new shoots that angle out from the stem that ended with the old flower.

New shoots will grow over the summer, set flower buds, and bloom the following spring.

Just after they bloom is also when you cut out unproductive, misshapen and obviously diseased stems to the ground. Twiggy growth should also be removed.

Thin and remove some canes to give proper spacing for healthy air flow, stimulating robust growth.

Lilacs of white pines, FlowerPatchFarmhouse.com

Cut out suckers straying to far from the plant, cut them to ground level. I have read that the suckers or shoots that maintain a pencil thickness all the way to the tip are the most productive but I haven’t tested that myself. Keep a good few inches between suckers or shoots.

Tipping

Tipping is when you cut back to a pair of side shoots instead of at the base of the spent flowers.

You will need to do this if you get a stem that shoots higher than the rest making for an uneven plant. The benefit of tipping is not only a well shaped lilac but the side shoots will put out new growth and flower buds for the following year.

I don’t give a particular month or date as the bloom time of your Lilac can be quite different than mine. Here we typically don’t see lilacs blooming until well into May while just 10 minutes down the road from me they bloomed in early April.

Thus the annual pruning time frame is different for each location.

The dwarf lilacs don’t need much pruning. Just dead head each year to keep neat and tidy. Miss Kim and Bloomerang Dwarf Lilac (reblooming)

I hope you found this helpful. I will try to get photos of each step in time. Or maybe a graphic.

Happy Gardening!

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Franziska Maria clematis in bloom, Flower Patch Farmhouse
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Sunflower

Thursday 8th of April 2021

The early blooming lilacs down the road might be Syringa hyacinthflora (search for cultivars Sister Justina, Mount Baker) or Syringa oblata. They bloom before Syringa vulgaris.

JustJessee

Friday 21st of August 2020

For those of us with two black thumbs, it would help if there were PICTURES of what to look for along with the text. Not everyone knows a "shoot" from a "sucker" (Me. Me is everyone.) What's a "dead head" exactly? Where you do you stop pruning on a 'dead head'....more images please.

Pamela

Sunday 23rd of August 2020

I will be sure to do that next Summer as it is too late now. A shoot from the ground is a sucker, just two different terms for the same thing.

sherry

Monday 1st of June 2020

This is great info Pamela, thank you very much! I have 17 French White Lilac Bushes planted across the front of my property - sandy soil - full sun - each bush was encased in a soil pod when planted. I had a green house do this professionally b/c I don't have a green thumb, so paid quite a bit, and it's so frustrating. They haven't grown very tall (as promised), and do not flower much (any year). Many flowers budded, but they didn't bloom ... we had a terrible cold spring here in the midwest, so all the to-be flowers simply turned black ... should I prune these off now? Basically they've never flowered like a lilac should, and they are growing slow. Thanks so much! (I also have done some of your art tutorials:).

Pamela

Monday 1st of June 2020

Yes, prune them now. It happens that way here at time too when we get a late hard frost, we either get no flowers or very few. This was a good year for them here, we had a mild spring with no late hard freezes. Sorry yours are not performing as you wished but they are rather slow growers in general so it just may be a case of patience for them to get as large as you want. I wish you better success with your lilacs. I am glad you enjoyed some of my painting lessons too. I have more coming but right now the garden takes all of my time.

Linda

Tuesday 28th of April 2020

My lilacs have already bloomed (sparsely) and I have never known to prune them. Is it too late to prune now, or do I have to wait until next year? Also, could you make your posts printable?

Pamela

Wednesday 29th of April 2020

You can still prune now and choose which prune to do. I will try to do an ebook or something similar for some of the posts but I can't make the entire thing printable. Sorry.

Norma

Tuesday 28th of April 2020

Thanks for the advice on the Lilacs

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