I believe the roots have rotted. To save this plant, you would need to break off the green parts of the rhizomes and lay them on the surface, buried about halfway, of an instantly-draining mix, NOT what looks like solid peat in the container now. A very shallow container is how I have the best results with these. I used the drip saucers that are always snapped onto plastic pots. As a succulent type plant, it needs to get very dry before adding more water. If the soil is soggy after watering, the rhizomes can rot, which is what looks like happened here.

add the photos into this post .. on a REPLY .... is that soil.. or potting medium??? if its soil.. that is why the roots probably rotted off ... as purp suggests in the other post ....potting medias most important function.. is water management .... and old media can wear out also ... ken

I think astilbe too. In fact it looks very much in form like my astilbe chinensis pumila does right now, flowers past, low dense growth.

Hoya bella, I believe.