Question
are astibes and asters acid loving plants?  

Answer
Hi Nina,
Thanks for your question.  Most asters will do well in slightly acidic to slightly alkaline soils.  Some asters will tolerate akaline soils well and others will not.  It depends upon what type of aster you have.  Neutral soils (pH of 7.0) are generally good for asters.  Astilbes will tolerate, even flourish in neutral to slightly acidic soil.  Astilbes do not like dry soil.  They like soil that is rich in humus and that is moist but not soggy.  In hot, dry climates, Astilbes benefit from afternoon shade and constant watering, as long as the soil is free draining.  They do not tolerate drought.  I hope this helps.
Tom