A number of different species with most of the plants offered being hybrids. Best in moist (not wet) soils. In the north they do best in part shade with more sun than shade and in the south they do best in more shade than sun, they are not full shade plants because they will not flower well with out good light, under poor light conditions they will grow into green clumps but flower poorly. The other condition that effects them is lack of moisture, they should have moist soils, especially before and during blooming. A nice Astilbe planting can be made by digging a hole and lining it with a plastic bag-make a few holes in the bag about half way between the bottom of the hole and the soil line, fill the bag with sandy compost/soil mix. Should only have to water once a week or less. Other wise they are easy to grow, with few pests and not often eaten by any thing. Can be divided every three or four years for best long term performance, dig clumps after blooming and cut into a few pieces and plant a little deeper and water well for a month or two. Heavy feeders that do best in rich soils.
Fresh seed can be stubborn to germinate but aged seed is not difficult.