I am having the same problem with my Salvia lasiantha in my greenhouse. That is caused by too sudden a drop in temperature, over several weeks. Late season salvias are acclimated to drops in temperatures, unless the drop-off is deeper and more rapid.

Now that the lasiantha has been in the greenhouse for a while, the dropping of buds has slowed down, and I am getting some blooms.

Decrease in flower size occurs both when the plant is trying to bloom in too cold as well as in too hot weather. Basically, this means that the sage is not growing in optimum conditions, which will vary from year to year.

OK. We have had some cool days and then some warm days. Hopefully that is it. The plant has tons of buds on it so maybe some of the later developing buds will not fall. Thanks!

I have the same problem! But it actually looks like something is eating the S. wagneriana flower buds... the leaves on this plant are also chewed up in one part of my yard (which is wet and shady), while S. wagneriana in another part of the yard is doing just fine, and blooming. It's like this really just happened "overnight"... last time I checked there were buds ready to bloom, today there is nothing. Snails?? Ugh!!

Check for caterpillars at night with a flashlight! I have been having the same problem with some of my other salvias. It's been really bad. I have had to go out and pull them off a lot! Also check under the chewed up leaves, the caterpillars like to hide there during the day.

Just wanted to post an update. The bud drop has subsided. I am posting a few pics. I had to stake the plant up since the branches all seem to hug the ground and the flower bracts are too heavy. You can see how much was lost because there are no calyces on that part of the inflorescences. The nice thing is that the inflorescences are over 1' long. Hope these pics work.