A bunch of plants stuck together?
That'd be an aquascape
A wabi kusa to put it simply is a clay ball covered in emmersed growth plants. These can be kept by beginners to experts and appreciated at many levels, be it the ease of care, the aesthetics, or the difference from the norm. They are simple and can be placed in an aquarium to create an instant aquascape or housed in a vase or bowl as an interesting piece to display or be the centerpiece at a dinner table.
The actual art of it is related to wabi sabi to quote wikipedia
Originally Posted by wikipedia
Characteristics of the wabi-sabi aesthetic include asymmetry, asperity, simplicity, modesty, intimacy, and the suggestion of natural processes.
They're pretty neat and I've been trying to formulate the actual substrate ball for a while now. I am determined to complete it in a few weeks.