Answer: Astilbe really need a fairly damp soil, kept evenly moist, to do their best. Although you have been watering, it may not be as effective as you think it is. On the other hand, if the soil is completely saturated and very wet, it is possible that there is actually too much moisture and this could also cause foliage problems. You might try digging down a bit to see if the water has actually soaked in deep where the roots are. Your goal is evenly moist yet not sopping wet. The soil should also be somewhat acidic and contain ample organic matter and be pretty rich for best results. Parenthetically, overfertilization could also cause foliage problems. There is also a possibility that there is a pest or disease problem. You might want to take a sample along with a photo or two to your county extension to see if they can give you a more precise diagnosis of the problem. In the meantime, keep the soil evenly moist and trim back the dead leaves. The plants should be able to regrow. Good luck with your astilbes.
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