I can offer no help, except to say I had astilbe ”Visions” similarly sited in my garden - north side of house, shaded by other plants - and I had absolutely zero blooms the year after it was planted (though it sure was blooming beautifully when I brought it home from the nursery the year before). The next year, I fertilized heavily and watered constantly and had a few paltry blooms. I do believe the Visions series needs more sun perhaps than some other astilbe varieties. In the end, I didn’t like it enough to keep trying, so I gave it the heave-ho. Interestingly, I planted corydalis lutea in the same shady location and I’m hardly getting any blooms from those either, guess the area is just too shaded.

I have 6 in my garden. Full sun (I know they are supposed to be a shade plant) and they bloom great although they do start to get a little sun burn toward the end of summer but what doesn't. They are at least 8 years old and I have never used fertilizer on them. And I don't water them much except maybe in long dry spells. I would stop using fertilizer and maybe move the one next to bush so it has room but I would think some shade is fine and probably a good thing.

think outside your box ...

that spirea could be tamed .. i believe some peeps cut them near the ground every year ... though you dont have to go that far .. and to be clear.. i would not shear it or give it a haircut.. i would hand prune it ....

otherwise.. your As look fine .. dont directly compare children.. they just arent necessarily duplicates of each other ... in this case.. i suspect a root mass difference.. for whatever reason.. but since besides being a bit smaller.. its not worth digging it up to look at the the roots or what shrub roots are under it ...

all that said.. move in spring or fall .. when nights get cool or cold again ...

i would say.. just about NEVER move anything in the heat of summer. aka july and augusst ... unless you just have to for other reasons ... or you live in say the PNW ... where 'when' just doesnt matter ...

ken.

I had a similar problem with my Peach Blossom Astilbe. First year it was blooming beautifully when I bought it. The next year the flowers were like yours, only much worse.

So I read up on Astilbes and learned they like a lot of water, so the following year I watered them every day, and I was rewarded with beautiful blooms.

Since then they've been fine, blooming every year, even when I've pulled them apart to divide them, and even if I don't water them every day.

Hopefully yours will be better next year.

Could be a water issue, even though you say the area takes some time to dry out. I've never had much luck with them in my garden, but I maintain a garden for a woman who basically has a swamp garden (literally standing water at times) and the astilbes do fantastic here.

I also think yours don't look too bad - foliage looks healthy and good imo. (Again that wilting on the one could be from lack of water??) Perhaps they need a bit more room. (but be careful of the timing if you decided to move them, in relation to temps)

What variety are they and how big are they supposed to get? Might there be varying sizes depending on variety?

:)

Dee