Lilac won't bloom

mstywoods(z5, Westminster, CO)May 30, 2014

We have a huge lilac bush (it's more like a tree as it's probably close to 15 ft or more tall and about as wide) that hasn't really bloomed the last two years. It's gotten a few blooms on mostly the new wood/suckers, but the main plant hasn't (it did bloom the first couple of years when we first moved here, but the last couple it hasn't). The tiny buds I see are either left over from previous year, or they are new and then dry up - not sure which.

I looked it up on google and found one page that mentions a reason may be that the plant is too old. In that case, you have to "rejuvenate prune" it. This would be a difficult task because of the size of the bush!

Anyone else have problems with their lilac blooming? Anyone else try pruning an older plant back and have success with it blooming again? I love the color and the scent of the blooms, so would really like to revive it if possible!


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Marj - lilac is a cane grower. You can chainsaw the whole thing down and in three years it'll be several feet tall and blooming again. I have a neighbor who has 20-year-old never-pruned lilacs that get fewer blooms and more powdery mildew every year - they just don't do well when they get that big and old.
Personal experience - we were going to take the one in our yard out so I chopped it down to 6" and tried to dig it up. HA! It's fully re-rooted and 4' tall three years later. They do bloom on old wood so yes, you'll need to wait for the flowers to come back. If you can't selectively prune I'd just lop it all back and be patient. :) Then you can just keep up on it afterward. I have a mock orange (also a cane grower) and after I took the whole thing down I now just prune out the oldest/wonkiest canes every 3-4 years and it looks GREAT.
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    Bookmark   May 31, 2014 at 9:34AM
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Yep, you have to hack it back! My old one barely bloomed the last two years. Last fall I cut what I thought was a lot of the larger limbs, (they say to cut 1/3 every year). It bloomed a lot better this spring, but I'm going to hack it again.

Good luck.

    Bookmark   May 31, 2014 at 9:36AM
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As others have said, you'll need to whack some, or all of it, back - with these huge bushes, it can be a lot of work, and then there's the issue of getting rid of all that stuff you just whacked off.

I've done pretty well by using an electric reciprocating saw and just getting the biggest 10 or so stems, then repeat that next year. That ways, the bush still looks pretty full. And that, you can chop up and they'll take it away with the trash.

I've also just cut them down entirely about a foot off the ground.

But I have a swamp where I throw all my shrub and tree pruning, I don't have to deal with getting rid of it via a bin by the side of the road.

At the end of the day, we have so many late freezes that we rarely get lilac blooms anyway, and then, 18 years ago I bought 50 lilac plants from the Soil Conservancy, so I'm now looking at 53 huge lilacs, and I just continue to look at 53 huge lilacs and if they get a few blooms, thats fine too. :-)

    Bookmark   May 31, 2014 at 10:54AM
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mstywoods(z5, Westminster, CO)

Thanks for all the info/tips/advice! When is the best time to cut it back - in the fall?

We just had to cut down the top half of a Russian Olive in our yard as that part was dead (still some suckers coming up, so the roots are still good - although I don't know that I really want it growing back. It did act as a bit of a screen from the neighbors, but hate the thorns on this tree!). What a job! DH used the chain saw to cut it down, and all the big branches into more easily handled size. Then DD and I broke down all the thousands of small branches off of the main branches. The plan was to then have these piles ready to load up in our truck at the next limb recycling day. But man - what a huge amount we ended up with from that top half of the tree, and many, many thorns!!! I put a ad on craigslist offering the dry wood for firewood or mulch material, and thankfully, many people have stopped by and have helped slowly dwindle down the piles :) Have one guy that has come by 2-3 times already and taken a med size truck load each time for using in his teepee up around Ft. Collins (interesting!). He emailed me yesterday and hopefully will be coming back this weekend to take the rest. That saves us a lot of work loading it up and making several trips to the recycle place!!

So because of that, not looking forward to another bunch of branches in the yard :( Hopefully cutting it back in Sept. would be a better time for the plant, as that would give us a rest as well as still time to get it to the limb recycle before they close for the season. This wood would be way too green for anyone to use as firewood!


    Bookmark   May 31, 2014 at 1:14PM
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mstywoods(z5, Westminster, CO)

So I found this site on pruning Lilacs: Looks like I can rest till early next spring!

    Bookmark   June 2, 2014 at 1:09PM
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Um, my lilacs have a stem mass of about, oh, 4 - 6 feet in diameter.

They graft lilacs? Who knew?

    Bookmark   June 2, 2014 at 2:27PM
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Skybird - z5, Denver, Colorado

Hi Misty,

This probably doesn't make much difference since yours is blooming very little anyway, but if you wait to cut yours down till "early next spring," as in before they bloom (or try to bloom), you'll be cutting off whatever flowers you might have gotten next year. Lilacs form the buds for the following spring shortly after they finish blooming in the current year.

Many years ago when "we" (ex and I!) bought a house in Olde Denver, the backyard was so overgrown we didn't even know what we "were getting!" When we cut down two very old and very overgrown spreading junipers we discovered we had a little pond! But included with the rest of the jungle was an apparently VERY old lilac that appeared to be beyond its useful life! Thinking we were "getting rid of it" we cut it ALL the way down, as Amy described above--less than a foot above the ground. I've always been into perennials as opposed to trees and bushes, so I was very surprised when it "came back with a vengeance!" Like Amy, ours regrew into a wonderful "rejuvenated" bush that you couldn't tell hadn't been recently planted after 2-3 years--except it was so much bigger because of the established root system the new growth came from. This was long ago, and I don't remember how long it took, but I believe by the third year for sure we were starting to get some nice flowers, on a bush that was still compact and pretty and required no additional pruning or care yet at that time. It sounds like David's system of cutting out the biggest, oldest, woodiest stems each year works too, and would continue to give you some flowers rather than having to wait for it to come back "from nothing" in the first couple years, but that would require annual maintenance. When we cut ours down we were just trying to get rid of stuff that appeared to have no value anymore, but in retrospect I'm glad we did it that way because it really did result in a very pretty "new" bush!

Whatever you decide to do, plan to do it NOW or else to wait till after it blooms/tries to bloom next spring. If you're going to cut it down all the way, the sooner you do it the sooner it will be able to "come back," so the sooner it will start blooming "fresh" again. If you wait to do that till next spring, it will be another whole year of "flowers lost" since it's not really blooming anymore anyway.

And I way second Amy's comment about the mildew too! The older, less healthy because of it's age, stems and foliage will be far more prone to developing mildew, and with such a "large thing" I'd be inclined to want to get it out of there sooner rather than later just to keep all that "additional" mildew out of my yard. The house I lived in (a rental) prior to my current house also had a very old, rarely blooming, lilac in the yard. Because I was renting I didn't cut it down to the ground (I did prune some of the big olde wood out of it), so it remained tall and always had quite a bit of old growth--and it was ALWAYS covered with mildew by midsummer! And with the "minimal" cutting back I did, it never did start to bloom nicely again like the one we had cut down all the way.

Whatever you decide to do, take some before and after pics and let us see how it's going,

    Bookmark   June 2, 2014 at 5:47PM
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mstywoods(z5, Westminster, CO)

Whooboy - not looking forward to this job!! Here's a few pics so you can see what I'm talking about:

Full "bush" - notice how much taller it is than our 6ft fence. I think my guess of 15 ft or more is pretty accurate:

Here's a closeup shot of the mass of stalks (notice the size of them next to my fingers):

And another of the main canes:

I gotta take some time to figure out my approach - a few canes at a time, or mass attack! I don't plan, though, to take it down to the ground in either case - it's too good of a screen from the neighbors yard! I may try just taking it down to fence level, as well as thin it out, and hope that's enough. If that doesn't help it bloom again, I may settle for that. Last year, I managed to dig up a sucker and get it to root, so hopefully at least I'll someday get blooms on that one :)

I haven't noticed the mildew on it, but maybe it's in the interior and haven't seen it. But I'll look for it now. I may just start whittling away at it slowly - since it only got maybe a handful of blooms this year, it won't make any difference as far as that goes for next year when I cut it back - but I thought that was so strange how it sets buds right after blooming for the next season! Wonder if there are other plants that do that.

Loved your story about your hidden pond, Skybird - that must have been a cool surprise!

    Bookmark   June 3, 2014 at 10:09PM
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I get mildew in September. Pretty much on everything, not just lilacs.

Your lilac is the size of my older ones. At the link is a reciprocating saw. If you don't have one, you might consider one - they're one great toy, and after you've used one, you're hooked. There are all kinds of other things they'll come in handy for -

For what its worth, there's a lilac down the road that is enormous, dwarfs the house its planted by - well over the roof, the crown in larger than the house is wide. And it blooms spectacularly any time we don't get a late freeze.

Here is a link that might be useful: saw

    Bookmark   June 3, 2014 at 10:23PM
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ZachS. z5 Littleton, CO

Off topic so I'm sorry...

Marj- Do you have any good thorny limbs from that Russian olive left? I need to build some fencing to keep critters out.....

    Bookmark   June 3, 2014 at 10:24PM
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mstywoods(z5, Westminster, CO)

ZachS - yes, still have some! The guy with the teepee keeps saying he's going to come and get them, but hasn't shown up again. So if you want some, however much you want is yours :) Send me a PM and I'll give you my address. Here's a link to the craigslist ad I've had going for awhile, with some pics of some of the wood: russian olive.

David - I think my husband probably has a reciprocating saw. He also has a chain saw. He is having rotator cup problems, so really shouldn't be trying to do something like this right now. I'm intimidated by the chain saw, but maybe I could handle the reciprocating saw.

Gosh, I sure wish mine would bloom like that neighbors of yours - it sounds like an impressive size!! Would love to see it. I wonder what the difference is between theirs and mine. Last year, I thought the weather was the reason ours didn't bloom. But don't think that was the case this year.

I'll be taking a look at what's behind mine and the neighbors yard. They do have a couple of large trees in that area, so maybe our lilac isn't as much as a screen as I'm thinking. If that's the case, then could take it down further.


This post was edited by mstywoods on Wed, Jun 4, 14 at 9:41

    Bookmark   June 4, 2014 at 8:34AM
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ZachS. z5 Littleton, CO

I sent you an email Marj! Thanks!

    Bookmark   June 4, 2014 at 8:11PM
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