Wabi-kusa is a quietly beautiful corner of the aquascaping world: a mound or ball of substrate planted with aquatic plants and moss, grown emersed, out of the water, as a living arrangement that can sit in a shallow dish or be dropped into a tank later. Moss is one of its natural ingredients.
What it is
The name nods to the wabi-sabi aesthetic of rustic, imperfect simplicity. In practice a wabi-kusa is a free-standing ball or low mound of soil, often bound with a little mesh or simply shaped by hand, planted with a mix of aquarium plants and moss and kept in humid air rather than underwater. The plants grow in their emersed forms, flowering and spreading in ways they never do submerged, and the whole thing reads as a miniature meadow.
Where moss comes in
Moss clothes the wabi-kusa as it does any hardscape, softening the base, knitting the planting together and holding moisture at the surface. The same aquarium mosses used elsewhere, Java and its relatives, take to emersed life readily and spread over the mound. Because the arrangement lives in damp air, moss thrives on it far more easily than it would on a dry surface indoors.
Making and growing one
Shape a ball of aquatic soil, sometimes around a core to hold its form, press in your chosen plants and a thin scatter of moss fragments, and stand it in a shallow dish with a little water and under a cover or in a humid spot with good light. Mist it, crack the cover daily for air to keep mould down, and let it grow in over several weeks; the technique is the same emersed growing described in the dry start method. Kept as a display it is an arrangement in its own right; dropped into a flooded tank, it becomes an instant planted scape.