What makes lilacs happy?

I have two very old lilacs, one syringa vulgaris and one probably Ellen Wilmott.

I've been working on them for three years now, pruning, fertilizing (lime, compost both years; plus superphosphate last year) coddling, and I don't feel they're getting healthier at all. Took out 1/3 of the oldest wood the first year, ditto the second as it said to do in various books.

They're looking really spindly and bloomed even less this year than the previous two, even though I dead-headed them carefully two years in a row. This year I didn't even bother, since it didn't seem to have helped at all.

Any thoughts?

Lilacs need a lot of sun and very good drainage. And dead-heading as soon as the blooms are spent is essential, since lilacs bloom on old wood. I dead-head mine as soon as the blooms don't look their best (a good reason to cut them to enjoy indoors!).

Sometimes you have to sacrifice a year of bloom when they get too spindly, in order to prune them into a good shape. Then you should see lots of blooms the following year. If you aren't having a problem with pests, I suspect they need a good haircut. I hardly fertilize mine.

I wonder if you're treating them too well? I don't grow lilacs myself, but I was reading another thread where someone was saying that they're supposed to do well with little care, no fertilizing, etc. So all the lime/compost/superphosphate might be too much for them.

Make sure you don't have holes in the stems- Mine was going gangbusters till this year and it has Lilac-Ash Borer. They say it's tough to get rid of, but I am going to try to cut out the stems with holes in the fall and dispose of them quickly. That way if any borers are inside they will be gone.

Thanks, all.

Hi again,
The serious lilac nurseries are a good place to consult- they are listed in the watchdog under Lilacs. They agree that lilacs need a pH of roughly 7 to do best, so you may have altered the pH of you soil with all the amendments you put in. Check your soil pH, and bring it back to near neutrality (I think as low as 6 may be OK). Also, to encourage blooms, use a food that has less nitrogen than phosphorus or potassium. Nitrogen is the first of the 3 numbers in a plant food's formula. Nitrogen stimulates growth rather than flowering. A food that's a 5-10-10 would be good; try a slow-release now, in fall, and again early in spring. One place, Fox Hills, sells its own lilac food.

I thought lilacs liked/needed wood-ash.

Am I going in the wrong direction?

Hi Constance, That I do not know specifically, only that the pH should be near 7 or a little lower. Check the big lilac nurseries listed in the Watchdog; one of them, the one in Quebec, is owned by the president of the Canadian Lilac Society, so I would read what he says about lilac cultivation. He's familiar with weather in the US; he ships a lot here and his prices are in US dollars.

I have a Mme Lemoine at least 10 years old (like yours, a double white) that was moved last fall when we re-landscaped. It's huge. It blooms pretty well as long as I prune right after blooming. One year I waited a bit too long and didn't have many the next year but only that once. This year I planted 3 old-fashioned types; they cames are bare-roots (more like bare sticks). It may be a few years until they bloom, but they are leafing out nicely, so maybe I'll get one or 2 next year. I used to have a Chinese lilac that was covered in blooms every year (the pruning took forever). I didn't care for the fragrance, so I chose not to transplant it along with Mme Lemoine. It was about as old too.

I think Lilacs DO like woodash...the very old ones should be cut to the ground (I am talking about the real old branches) and leave the rest.

Levilyla, I'm curious about the woodash because I never used it or saw mention of it. Do you give your lilacs woodash? Do you give them anything else? Also, when you cut your lilacs so much, when do you do it? I've never cut mine that drastically. The trunks are too thick for that. I'll cut roses and quince that much. Tell us what kind of lilacs you have.

Now you are going to laugh...I have NO Lilacs. They like (I have heard) woodashes..(lime)...also if it is a really old Lilac I have heard to cut the very old branches to the ground to rejuvenate it. I have not enough sun for them but O how I wish I did.

Levilyla, maybe dwarf lilacs can be cut all the way down but not regular ones- branches come out of a thick trunk. You can prune branches back on young and old lilacs, but if you do it after buds have set, you'll lose the blooms for the following year (they only bloom on old wood and begin setting next year's buds even while blooming). But I never heard of wood ash for them, and this is my second house with lilacs.
You don't have one little patch somewhere in your yard that gets 6 hours of light? I bet you do have a little patch big enough for a lilac bush somewhere. You're in Bawlmer, and that's where I'm from (Liberty Heights area). When I was an undergrad at Hopkins, the lilacs by the tennis courts facing N. Charles St. (just above 34th St.) would bloom in late April and the smell was heaven on earth. Those gardeners at Hopkins really knew their plants. The azalea gardens were amazing, the quince hedges spectacular, the dogwoods bloomed on command. The only thing they couldn't do is keep the huge magnolias lining the quadrangles from blooming in mid-March, right before the last freeze!

The lilacs we had in Illinois were by our neighbor's driveway between the houses. They were in shade for quite a bit of the day, and they did quite well.

"I would like to try a dwarf Korean Lilac (maybe Miss Kim). "

Miss Kim gets 10' x 10', so not so dwarf.

LOL..okay which one should I try?? My daughter in law has Miss Kim and it seems quite smaller than most of the "regular " ones... blooms etc. She has had it about 5 years now.

Syringa meyeri 'Palibin'
Syringa microphylla 'Superba'(many sites say best in partial shade)
Tinkerbelle
Prairie Petite
Red Pixie

Eric at www.lilacs.com is the expert on this group. He used to post at GardenWeb--he was quite helpful. He always told the story about the original Miss Kim plant, and how it was well over 10'. He now says 10'-12'. Try this page for a list of cultivars and sizes http://www.lilacs.com/lilacs.html

Thanks so much Kevin...I love the thought of the one that says partial shade.

I'd read that to rejuvenate old lilacs you take out 1/3 of the oldest wood each year--I've done that for two years now. Last year, the blooms were ok--this year, even though I'd carefully deadheaded, the blooms were pretty pathetic.

I'll pick maybe six suckers each plant to let grow, and prune the rest.

Our soil is generally acidic, which is why I've limed and woodashed. Maybe I've gone too far.

I do have an impulse to throw some superphosphate in there, though. Perhaps just from frustration.

Glad you started this thread! I just rescued 6 - 1/2 gallon pots of Miss Kim from the Dead & Dying table for a little over 2 bucks each. An hour soak in some water and low and behold, they all look alive and perky. I hope they REALLY like full sun, because it's pretty intensely sunny here in the High Desert :-) ... And, of course, there is always the gamble with Wally Mart that while they might actually be lilacs, they may not be Miss Kims... still, if they live and they are lilacs of some sort, I'll be happy :-)

Constance, check your soil pH, you may have made it too alkaline. If so, add an amendment to bring the pH down (the hydrangea thread has info on that). I'd also add a fertilizer for blooming (high middle number).
I prune mine to where it's manageable, whether it's a 1/3, more or less doesn't matter, but I prune to near a leaf node so it'll be stimulated to set a new bud.

Too alkaline? Never thought of that. It's so acid here, it never occurred to me I might have overdone it. I'll test ASAP.

I thought Lilacs liked a less acidic soil.

I sprinkled a 1/2 to 1 cup of wood ashes from our outdoor firepit around each mature old fashioned lilac and the French hybrid lilac last year. I think 1 cup is too much as I saw some leaf curling - and I attributed it to the ash but not sure. This year they look better. These were horribly overgrown and leaning to the light. I've taken 3 years to cut them down the old wood almost completely. We took down several trees that were overhanging them also. They are now resprouting back in a vase shape and not leaning so badly. They haven't looked too great the past few years but I fertilized, mulched, pulled up the landscape cloth the former owner had down and sprayed with Messenger. They don't get as much sun as a lilac needs but its close.

Levilyla, Lilacs like a soil that's slightly acidic to close to neutral (pH 6 to 7). Most people have acidic soil, probably why the recommendation to put wood ash in. But you should not change the pH if you don't know what you started with; pH may have been fine and the problem may reside elsewhere.

I've read that lilac leaf curl is usually attributed to air pollution.

We live in the burbs, cars pass our house intermittantly during the day, the lilacs are fine, our air quality is rated acceptable over 95% of the time. The only time I see leaves curling is when they need a drink. Then the leaves uncurl. Your lilacs are old, they should be acclimatized to your area. If I have a really wet summer, I may see powdery mildew in August. That hasn't happened in a few years. There's also a bug that causes it (I've not seen it):
http://gardenline.usask.ca/pests/lilac.html so you can check for this bug and use a spray.

Really, the lilac nursery folk know a lot about lilacs and how to keep them happy and in bloom. Send them you questions and report back to us what they replied. Kevin_5 gave the url for one in the NE US above, http://www.lilacs,com.
Here's another link to a major lilac grower: http://www.spi.8m.com/





This message was edited Jul 30, 2006 11:51 AM

Hi! Just stumbled onto this thread, wow, great info here, thanks everyone. Lilacs grow very well here, and we have fairly alkaline, clayish soil. I know they tolerate some shade as well. I would like to plant a lilac standard, you know, like a tree only with a bush on top. My guess is that these would be dwarf cultivars, does anyone here have one? I want to plant it this fall, but will wait until spring if I have to.

Has anyone heard yet what the lilac impact is expected to be from emerald ash borers? I heard that in China they attack some other genera, like Pterocarya, so I bet they might go after ash relatives like Syringa, Ligustrum, and Forestiera -- ?

Guy S.

Kill joy!

Really? That's terrible. Well, I hardly expected it to be a long term investment. But still. Thanks for the warning Guy.

Hey, go for it anyway. You can always treat a single lilac stem if you hafta. I was just curious about the potential borer problem.
-- Killjoy

I was more curious if anyone has ever tried growing one of these?

Does this one count?

Guy - what is that? Did you prune up the standard? It's a beautiful specimen - I like the setting too.

The ash/lilac borer Podesia aureocincta is sometimes confused with the much more serious emerald ash borer. I believe the pest can be eradicated with chemicals and/or pruning out infested wood. In these parts the public is confusing any borer with EAB. There are probably gonna be a few salvageable lilacs bite the dust as a result.

I did a thread on it a few months back but I don't recall the title now -- or maybe I just stuck it in someone else's thread, I dunno. Anyway, it was planted in 1875 at my wife's ancestors' house, and I transplanted it from central Iowa to central Illinois in 1988 with a 5000-pound hand-dug rootball. It's a common lilac, S. vulgaris, and that's the view from my front door this past spring. VV actually still has the 1989 issue of Fine Gardening that featured the transplanting.

Guy S.

I was typing over Snapple, sorry Snapple! We do trap for Podesia here and spray as soon as we collect the first males, usually mid-May. My question was regarding the potential for EAB to jump into other genera like Podesia does, since it's already known to jump into other families.
Guy S.

Hey, quite all right there StarhillForest. In NW Ohio there has been no notice of EAB in Syringa ----- yet. It may be because the preferred host is still plentiful. However that could change as the ash die off. In 5 to 7 years from now (maybe sooner) there won't be an untreated ash left standing in this region. And there will be darned few treated ash left either. The state of Michigan has the best information available on EAB and has the best research protocols currently in place, although Ohio is beginning some nice research of its own. Ohio came to the party a little late and wasted a ton of taxpayer's dollars on a strategy that doesn't work. Those interested in the most current info on this pest can check the Michigan stuff to stay abreast of what is coming their way. Incidentally, early results from the Ohio tests indicate that imidacloprid is the most promising treatment on early borer infestation. I have to wonder if that same chemical would also work on Podesia in Syringa and spare the plant from pruning out infested wood. My one lonely lilac did have a borer some time ago. One cycle of spraying and a simple pruning eliminated the pest and it hasn't returned.

Nice thought, but Podesia is a clearwing borer and apparently not affected by Imidacloprid. EAB is closely related to bronze birch borer (same genus -- Agrilus) and reportedly can be controlled by Imidacloprid if you can get enough of the material into the area being eaten.

Constance, I guess I've stolen your thread, sorry. But the EAB relevance to lilacs, if there is any, would be something you would want to know about.

Guy S.

Good point StarhillForest, and correct. I am thinking nuclear might be the only true deterrent to EAB.