Pumice

Typically part of a soil mix, e.g. 1:1:1 with Akadama & Lava.

Provides aeration to the roots. Ideal for Yamadori (collected) trees that lack sufficient roots. May be 100% pumice.

Must sift and rinse off dust or finer particles, as these can rinse off in the pot and create a cement-like barrier that limits drainage.

Compared to Akadama or less so Lava, Pumice does not retain water or nutrients (i.e. liquid fertilizer)—so repeat watering or fertilizing is needed.

Pumice is lighter in weight, so helpful when moving grow-boxes or large pots.

From Facebook Boon post:

“I grow everything in pumice. Sift it to remove all fines and grade it to sizes. The smaller particles hold more water longer. Larger particles for larger pots and more mature trees. I use some sphagnum moss for top dressing during the arid summers here. The fines are good for starting cuttings.”

Michael Weipumice, soilComment