Hi Lori,
I dont know this brand of fertilizer, but as a general rule it is better not to give them fertilizer at the start, the idea being that they grow a larger root system when "searching for food". And if you have an average garden soil they should be okay for the first year anyway. And if you could bring yourself to pinch off most of the flower stalks/ seed heads, you encourage the growth of the roots further. I would add some compost or leaf mulch next spring as they are a kind of woodland species and love soil with lots of organic matter. Watering: try to douse/drench them about once a week, so the water percolates really deeply into the soil instead of some daily watering which results in a shallow rootsystem.
Happy gardening, cheers, Lin

Lori,

Astilbes in our zone and area (northeast) are tougher than most folks think. They are one of the 'mainstays' of our gardens here and will be found in deep shade and full sun.

Aside from the great tips offered by Lin, I would add that it is good to divide them every fourth year or so.

I wouldn't fertilize them this year either. I would, however, keep them well-watered, astilbe love water and the leaves will dry up and brown without enough.

Karen

Thanks, guys!

The garden center recommended them for a couple of tricks spots in my perennial bed - I've got a west-facing wall that gets plenty of afternoon sun...except for the parts that are shaded by bay windows and porches. That's where the astilbes have gone. I put some osmocote in the planting holes, but I'll leave off any extra fertilizing this year - and thanks for the tips on watering and mulching!

Lori

I've never fertilized my astilbes, and they seem happy as can be... but they're in the wettest part of my garden (after a hard rain, there's often standing water for about an hour). I agree that water is key to their success.

I don't think anyone's mentioned, so I will -- if they do dry out (as mine have during a heat wave while we were gone on vacation), that's it for the foliage for the year. I've not killed one with inadequate watering, they've all come back the next year, but they will not regrow new foliage once they brown up.

"... they will not regrow new foliage once they brown up." Yes they will. I rescued 5, each in their one gallon pot from a box store a couple of years ago. They were actually given to me since the manager thought they were dead. Brought them home, removed all the dead foliage, soaked the roots for an hour and planted them. Within two weeks the foliage was coming up gangbusters and this year they were all divided to sell at my annual plant sale. :O)

I like to fertilize my astilbes with composted cow manure which I get at the garden store. They will bloom like crazy the following year. I think you could use Neptune at half strength once they are a bit more established.
Keski

I have never fertilized astilbes. Had the same experience as tiffy, bought sad looking plants, trimmed the dead stems down and they regrew. Also have had older ones regrow in the garden. They are loving the heavy rains we are having but we are wishing for good weather!

The wall is west facing, but portions of it are thrown into shade by porches and bay windows - I put the astilbes in the shaded spots. They're bridging a space between Hosta Land and Daylilies - I had daylilies there before, but they were spindly and failed to thrive (not enough sun).

I wonder if the key to rejuvenating dried up astilbes is to remove the dead-ish foliage? I know that if my daylily foliage gets damaged, that's it for the year...unless I cut the thing back almost to the ground, in which case it will start putting out new leaves almost instantly. It is an explanation that would reconcile the different experiences that people seem to have had with this.

Am making sure that the astilbes are getting hand watered daily, what with the scorching dry weather we're having here right now!