Lilac Problem

My lilac bush does not bloom. It is 5 years old and gets a half a day of sun. Last summer I had one flower 1/2 " high and nothing this year. What am I doing wrong?
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b



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Have you tested soil pH? Lilacs prefer a sweet soil, 6-7, I throw a cup of lime on the rootzone each year and get plenty of blooms (my soil is naturally very acid, 5 or lower).
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Ann, gardening in Zone 6a
South of Boston, Massachusetts
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#1 cause of failure to bloom is insufficient sunlight. Ideally they have morning AND afternoon sun; morning sun alone could well be insufficient. Six bright hours is the minimum, longer would be great. If the shrub isn't getting enough sun, no matter what else you do for it it won't bloom.
#2 reason for never blooming is their narrow environmental requirements aren't met. They need very warm summers with lots & lots of sunlight, then a good solid wintry winter for dormancy; they like rather northerly climates with summer sun still shining at nine at night, followed short winter days, like in central Europe or the Pacific Northwest. If conditions are too even year round, especially the older cultivars will forget when it's time to bloom (newer varieties are more forgiving). So some of the commercially prepared plants are grown where they get exactly the seasons they want & are quick-shipped to market as soon as buds are big, & people buy a plant in full flower -- but it's the wrong zone & though it won't drop dead it won't bloom again either.
Other possibilities:
They set buds a year in advance, & untimely pruning can remove all the next year's flowers. Correct time to prune is immediately after bloom, as they set new buds the summer after blooming. Pruning in autumn, winter, or spring removes those buds.
Fertilizing with nitrogen-rich fertilizer can stop them from blooming. Kelp or bonemeal is about as much fertilizer as they can stand.
So too overwatering can stop them from setting buds. Sometimes worrying about a shrub causes a gardener to take extra special good care of it, meaning watering it way too often & overfertilizing, when it would more likely thrive on neglect.
Ours do fine in our naturally acidic soils, but sometimes they don't, &amp if soil is too acidic it might slow them down, & feedings of lime or wood-ash can help them flower. But don't lime the soil without knowing the pH as if it doesn't need lime it seriously doesn't need lime.
A shrub planted too deep in the ground will not bloom; it should be planted on a little hump.
It's rare that lilac buds freeze off, but if there is a harshe late freeze that hits the buds just as they come out of dormancy, they could all be killed.
There MIGHT be nothing wrong. If your shrub is really only five years old total, it would not be at all unusual that it didn't bloom until it was six years old &amp of substantial size -- it normally takes to to five full years before they bloom at all. Even somewhat mature lilacs pot-raised frequently take three to five full years to "settle in" from the shock of being transplanted into the garden -- six or seven years would be an unexpected length of time, but five is just within the normal range of adjustment.
-paghat the ratgirl
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wrote:

I don't understand why short winter days would make any difference since lilacs are deciduous.
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Photoreceptors are also present in the bark of many trees & shrubs.
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David J. Bockman, Fairfax, VA (USDA Hardiness Zone 7)
email: snipped-for-privacy@beyondgardening.com
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Well, it's a corollary, although not necessarily an obvious one, that long summer days (of, say 16 sunlit hours) must exist only in places with short winter days (8 sunlit hours) . Many lilacs are native to Eastern Europe - places like Yugoslavia, Romania, Hungary. The latitude there is between 45 and 55. This is the same latitude as the northern tier of states in the US, all along the Canadian border.
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By the way, and this is partly to defuse the little uncomfortable exchange on this thread - scientists seem to have established that the date lilacs bloom in a given location is predictable to a precise degree - based on degree days above 40 - or in some versions, degree days above 33. Here is a typical description: "Bloom time data on the Hort. Farm lilacs was collected in 1978 -79. Bloom period and degree-day accumulation to bloom was presented in UVM Agricultural Experiment Station Research Report 1, 1980, entitled "Flowering and Fruiting of Woody Ornamental Plants in Vermont." To calculate the degree day accumulation before bloom we used the accumulated average daily temperatures above the base temperature of 40F until bloom. For example, a day with maximum temperature of 60 and minimum of 38 would result in average temperature of 49 giving a degree day accumulation of 9 degree days. The earliest blooming lilac cultivars -- 'Evangeline', 'Minnehaha' and 'Lucie Baltet' commenced bloom May 10 in 1979 with a degree day accumulation of 350. The latest to bloom were Preston hybrids 'Nocturne', 'Miss Canada' and 'Elinor' which commenced flowering on June 5 with 911 degree days accumulated. Using the degree day data, one can predict the date of bloom for various locations for each cultivar for which we have data. "
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snipped-for-privacy@netscape.net (paghat) expounded:

I guess all the lilacs I've seen around here in partial shade or planted in a dooryard getting only partial day sun haven't heard this rule yet. Yes, the prefer sun, but they do find with part-day sun and filtered shade.
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Ann, gardening in Zone 6a
South of Boston, Massachusetts
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The newer cultivars are the most forgiving. But if you're merely telling us that in Ookook Land nobody has has ever had any trouble getting lilacs to bloom, then wow, that's such very special place.
-paghat the ratgirl
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snipped-for-privacy@netscape.net (paghat) expounded:

Lots of newer hybrids planted in dooryards of 250 year old colonials.
I identify where I garden, it's hardly an unknown area. Where you are lilacs may need more sun because they don't get as much in the rainy northwest - unless you're on the lee side of the mountains.
I'm pointing out the fact that there are numerous reasons why lilacs don't flower, one of which is soil pH, the usual case around here in acid-soil New England. You have experienced the lack of sun thing. Different environments, different outcomes.
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Ann, gardening in Zone 6a
South of Boston, Massachusetts
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Too bad you're just being snotty, as otherwise you would finally have spoken the truth. If you are seriously claiming the lilacs in your neighborhood are a quarter-millenia old, why wouldn't I believe you? Could it be because lilacs never live that long & the oldest lilacs in North America are a mere 120 years old on Makinac Island?
While wild shrubs were brought to North America in the early 1700s (at which time they were planted primarily in graveyards) virtually all garden or front-of-house cultivars presently grown, if they actually are the oldest ones, date only to the 1880s-1920s. There ARE still a very few thriving thickets of true wild non-hybridized lilacs dating to the early 1800s in the Northeast, & to the 1840s or 1850s in the Northwest -- not individually old trees like those profound rarities on Makinac Island of course, but continuously renewed from suckers & seeds -- none of these thickets are in peoples' front yards even if the houses are built on forgotten graveyards, because naturalized wild lilacs need acres of space & no other cultivation in the vicinity to perpetuate themselves.
If you were a credible witness I'd be truly excited to learn about that magical colonial neighborhood devoid of modern cultivars (which begin in Victorian France & began arriving stateside in the 1880s), a neighborhood which did not participate in the first wave of serious lilac popularity during the fin d'siecle, but have instead preserved for a quarter-millenia only the descendants of natural wild graveyard plants just like those from Transylvania. If it WERE true you shouldn't be kvetching at me for disbelieving in the little town where time stood still & you can get a free melmac plate-set with every tank of gas & a flophouse bed for a nickel a night; rather, you should be writing it up for the horticultural journals, because it's honestly too darned cool. Just don't add the part about them blooming in the shade or the editor will know you're makin' it all up.

Making this up as you go along? Don't tell anyone our secret because we already have too many moving here, but it scarsely ever rains here in the summer, but only autumn through spring. The Northwest is great lilac country, & there's hardly a block in any town on Puget Sound without several. The sun goes down after nine o'clock at night at high summer, so the lilacs just bask & bask developing their buds for the following spring.

Actually my original post noted several & probably all the possible reasons for failure to bloom including acidity as an occasional cause especially for those less forgiving early cultivars -- plus I concluded with my sense that three to five years is a NORMAL length of time for a some baby lilacs not to have bloomed, so there MIGHT not actually be a problem. I think it was a good post that insists on no single answer but gave enough info to assist anyone trying to figure out why THEIR particular shrubs haven't bloomed.
But you seem to have read only as far as the #1 cause of lilacs failing to bloom -- then you strangely began to allege that the lilacs in your neighborhood are 250 years old & bloom in the shade -- which even if you hadn't made that up wouldn't change the broader realities I outlined.
-paggers
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snipped-for-privacy@netscape.net (paghat) expounded:

Wow, try reading for comprehension next time. Oh, that's right, you don't have to, because you know just *everything* there is to know. It's amazing the gardening world got along before you (and will continue without you seomday).
You said newer hybrids. I referred to old stand lilacs, of which there are many, in the New England Area. You, however, like to get on your very high horse and pontificate to the point of lunacy, exaggerating and spewing, diarrhea of the fingertips, blah, blah, blah. Now do dribble on, I'm done with it.
--
Ann, gardening in Zone 6a
South of Boston, Massachusetts
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(paghat) expounded:

Oh my god, I haven't been on here for years. I scan down, open a post and its Ann from Massachusetts. It must be 4 or 5 years since I stopped by here and you are still at it, being a nasty, know it all bitch. I would have thought a house would have fallen on you by now. Must be a very sad life you have lead.
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"paghat" wrote

Great information and worth saving. Our lilac bush has been planted for quite a few years (7 or 8) and this is the first year of prolific bloom. I do have questions, though. There's a heavy undergrowth of new shoots - should these be removed at (or below) ground level, or even removed at all because they will replace old growth - and when (and if) should old growth be removed to encourage flowering?
Dora
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->snipped<-
AN>Have you tested soil pH? Lilacs prefer a sweet soil, 6-7, I throw a cup of AN>lime on the rootzone each year and get plenty of blooms (my soil is naturall AN>very acid, 5 or lower). Our double blossomed french blues flowered beutifully yesterday (May 12) here in Medford, in Middlesex county. How about yours?
Ciao, Ack.
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Perhaps you are an overdiligent pruner? I recall reading newspaper articles years ago in which gardeners were warned not to prune off certain twigs that are near the flower points, because that is where next year's blossoms grow. Some people were removing theses when they deadheaded.

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I have never pruned them

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