Dan is correct. Seasonal weather, typical watering frequency, soil drainage (i.e., does water pond around it?) or other problems like compaction or nutrient deficency, pruning method (if any) and time of pruning, insect activity (if any) in both the previous year and this one, possible girdling by a weed eater or lawn mower and so on can all have an impact on blooming. Having said that, Ivory Silks have had a great year here in SC KS. Can you provide any more info on any of these things?
hortster

They're lighting up the neighborhoods here too, hortster, best in some time.

Dan

Improper planting, I doubt very much. I research this tree before I bought it, I wasn't about to spend a lot of money on a tree that won't do well in my area. I have clay soil but used compost and top soil to fill in the hole when I planted it. Due to all the rain, I have yet to water. Its on a slight incline so water doesn't pool around it. I don't use a weed eater and the plastic mulch ring keeps the weeds under control so the lawn mower doesn't go anyway near it. I put a plastic guard around it during the winter to protect it from hungry rabbits. It get sun in the morning and early afternoon. I also talk to the Johnson county garden extension office because they have one. But I wasn't satisfied with the answer.

Its seems the more info you supply the more of mystery it becomes, lol.

I have the same issue and no resolution.

Lilacs even in the most disatrous situations have bloomed prolifically around here.

Since my cultivar (Summer Snow) blooms later than 'Ivory Silk', late frost is the only thing I can think of.

I also have ants in and around the root system but based on the research (and identifying the type of ant) I can't say they are the issue.

Does it grow much?

"I have clay soil but used compost and top soil to fill in the hole when I planted it."

Could be the source of the whole problem. Never replace the soil in the planting hole. You have created a bathtub in your clay soil.

I have clay soil but used compost and top soil to fill in the hole when I planted it.

Yup. Improper planting. That's probably 85-95% of the issue.

Dan

Syringa reticulata tolerates clay soil very well, as well as compacted soil.

They do poorly in water logged soil as it needs to be fairly well drained.

If your experiencing the "bathtub" effect this tree will hate this more so than other trees.

This is my fault as I should have the read my response before I posted it. But the libray was closing and I was running out of time. Whenever, I plant anything. I put a mixture of topsoil, compost and the original soil that I dug out. That way I don't get the bathrub effect which would kill most of my garden, the other trees I planted which bloom just fine and my all roses. Other thing, is I also use earthright once or twice a year. I haven't yet this year but I have to this month or I have to wait until fall. Like I said I did talk to Johnson county garden extension office that told me that it might be growing issue. As the tree has really taken off in the last two year. The other times it didn't bloom were to late freeze but this year that shouldn't been an issue. In early May the lowest we got was 38 which did affect some of the leaves but not enough to keep it from blooming. There are some blooming in a near by city. Ants are not an issue because they prefer my Pin oak.

Anything ever happen w/ your tree? I have had the same problem for 2 years now. First 3 years bloomed, and now nothing, growing great, just no flowers. Have clay also, my neighbors blooms just fine.

If growing great, then nothing to worry about, it'll do it again in its own time, as long as not a lot of shade creeping up on it.

I had a similar issue with my 6 year old lilac. Bloomed first 2 years, then only a single bloom on the entire tree each year, teasing me. Clay soil, shade part of the day, soil is pretty dry and I didn't water it much. This year I got dozens of blooms, more than I have ever seen on the tree. This is what I did: last year I pruned the end points of majority of branches BC they were dried up/didn't have leaves. I got a bunch of compost and dumped it all around the root area (2 foot radius). I watered it like crazy all spring since I planted some grass near by so was watering anyways. Not sure which of the above did it but it worked!