So glad you posted this. My astilbe grew with almost a ruñner habit, intertwiningwith my heuchera. I grew them very successfully in a previous home. No idea what is happening now.

There could be any number of reasons to explain the problem--poor soil, insufficient water, predators. Lots of astilbes have thrived where I am in your zone so I'm guessing soil is probably at fault for yours not doing so well. My own are doing well in slightly acidic, sandy loam in full to partial shade. For some reason this seems to be a down year for their blossoms altho' a few varieties are apparently thriving.

Keep in mind that thanks to weather conditions, many times perennials have good years and bad years. A gardener learns to accept both rather than expecting a garden to perform exactly the same year after year. This year my Hellebores/Lenten roses produced nearly 50 blooms whereas I was lucky to see less than a tenth that many last year.

Don't rule out/ignore adding/incorporating other shade-tolerant perennials in your shady garden beds--Tricyrtis hirta/toad lily, Polemonium/Jacob's ladder, Alchemilla mollis/Lady's Mantle, Aquilegia/columbine, Mertensia virginiana/Virginia bluebells, Hosta, Dicentra/bleeding heart, Brunnera/Siberian bugloss, Heuchera/coral bells, Pulmonaria/Lungwort, Chelone/turtlehead & Cimicifuga racemosa/black snakeroot, Atherium japonnicum/ Japanese painted fern & Japanese sedge grass. They'll provide both foliage & color contrasts.

The majority of the plants mentioned above can easily be grown from seed via winter sowing or else by division + you can trade for seeds on the Seed Exchange forum.

It's been my experience in recent years that gardening doesn't need to be terribly expensive I you're willing to work hard.

Thanks, gardenweed - better luck next year I guess. I will mix more vermiculite etc in the soil as that bed has a lot of clay underneath though I've improved it. The white astilbe and an older pink and a red are flourishing (flower stems strong) in the same bed, as are the other shade perennials there & in next bed (most of what you list above), so I will just be patient. I'm having a great time with this, regardless!

Trans Terp,
That is a beautiful spot! What trees do you have providing your shade? I'm wondering how much leaf cover you get in autumn and if you clear them away or allow them to decay. I have a ton of oaks and get heavy leaf cover that I have cleared the past two seasons. My neighbors wouldn't tolerate a totally natural look.

Martha

Trans Terp

Ditto Martha's comment--very pretty aspect. I'm fortunate there are few trees to interfere in my gardening efforts since I've been planting here. I designed all my formal beds on paper before ever jamming a spade in the dirt but was grateful at the time that I didn't have to factor in tree roots or autumn leaves. Even now, thanks to the devastating October 2011 snow storm, I have far fewer trees/leaves with which to contend. That event reduced the amount of shade in my garden by two thirds.

Most of my astilbes were grown from bare-root specimens purchased at big box stores so I can't be 100% certain which varieties they are but none have ever displayed weak flower stems or plumes, even during extended dry seasons.

"I purchased some astilbe starts...."

I gather from your post, this is the first year for these astilbe. It may simply be they aren't established enough to bloom properly. A plant really needs to be fully established before you can pass judgement on how it may perform in the future under your conditions. For instance if you planted them a bit late and they really didn't have time to establish a good root system before all the top growth commenced, I wouldn't expect very good flowering the first year. Give 'em another year.

However, it could also be a matter of too little light. You didn't indicate how much shade these are in. In my zone at least, astilbe are not a plant for deep shade. As long as they have enough water, they really do well in at least 1/2 day sun, but again, that's in my zone. I've never gardened in yours.

Kevin

Aachenelf, you're probably spot-on. It's probably because they're young and need to mature to strengthen. I just need to be patient! Docmom, we have a variety of deciduous trees and each spring I have a lot of leaves to clear, sometimes by hand to protect all the beautiful shoots coming up. The underlying humus is wonderful in that basin - the other beds, around the house, are harder clay and take more work. All the mature hostas were already here when we moved in, though we have moved many specimens around to 'build' the basin and other beds according to sun & soil. Thanks all!

FWIW, they do like consistently moist soil.

SLUGS and/or SNAILS is the culprit here. They trail up the flower spike at night, which snaps off or bends off the flower spike at its tender spot. Get rid of the slugs and snails and this won't happen anymore.