Wabikusa is a kokedama, a ball of soil covered with moss, but with semi-aquatic plants.
Why aquatic? Because they are so easy to use, any part can be snipped off and replanted, and if you spot any aphids, you can submerge the wabikusa in bucket of water for two days to kill off and wash away all those insects. And they flower too! Just keep them always moist and nourished, an orchid fertilizer does the deed.
String moss and hair grass (eleocharis), this ball is the one from last year. It was full of river buttercups and forest moss that gradually got replaced by an aquatic species.
With some rotala strands and ranunculus inundatus.
This one is very young and still undergoing the transition from very moist air to a dryer one. Made with hydrocotyle tripartita, proserpinaca, limnophila and hemianthus. The little clover leaves are marsilea hirsuta. You can even see the pins that I use for the hydrocotyle runners:
And a fragment of someone else's wabikusas:
Do take a look at that gallery, they are absolutely stunning!