Lythrop

This hardy plant would grow in the Nether on any exposed surface of a block: top, side, bottom.

                Based on the real plant, also called living rocks, they will sit on the block similar to the way sea pickles or turtle eggs do. They would be placed in groups or individually.  They would use a tick count cycle to switch between ‘in bloom’ and no bloom so for a short period they would burst into yellow blooms.