Pumice Grow Media for Bonsai Soils


attractive bonsai tree caring for bonsai leaves

Lightweight and airy, porous pumice stones are riven with nooks and crannies that hold nutrients and support beneficial microbes and mosses, yet are free of fines and sized to drain predictably.

photo of Rutsu Eights pumice grow media

Rūtsu Eights™—a blend of 3/8 to 1/8-inch cleaned and dried pumice stones.

photo of Rutsu Sixteenths pumice grow media

Rūtsu Sixteenths™—3/16 to 1/16-inch cleaned and dried pumice stones.

photo of Rutsu Fines pumice grow media

Rūtsu Fines™—1/8-inch stones to powdery, water-retentive pumice fines.

rutsu bonsai soil logo

PUMICE HAS BEEN USED for a long time as a soil or a component in a soil blend by bonsai enthusiasts. There seems to be almost as many bonsai soil blend recipes as there are enthusiasts, evidence that no single media works for all trees at every stage of development and in all conditions. Bottom line: the soil components themselves must be selected and blended with an understanding of what best suits a particular tree in terms of drainage and water retention needs. Improper watering—an improper balance between soil, tree type, container, and water—is the bane of successful bonsai. For most trees, the ideal balance is achieved when the tree needs water every 24 to 36 hours.

Our Rūtsu™ pumice grow media (pronounced root-sue) is available in three grade sizes to meet the specific and variable needs of individual Bonsai plants. This provides the bonsai enthusiast with the flexiblity to compose the ideal inorganic component of the soil blend for each tree in their collection. The Rūtsu Eights™ and Rūtsu Sixteenths™ grades are dried, screened and graded to contain no fines. The Rūtsu Fines™ media provides the grower with a way to blend the precise amount of pumice fines into the other grades if and as needed to meet the water needs of a particular tree.

Pumice Stone Media

Pumice is abundant and found in many parts of the world, but not all pumice is created equal. Rūtsu™ pumice media comes from a pumice deposit located in southeast Idaho on the shoreline of an ancient lake known as Lake Bonneville...a vast, freshwater lake that once covered much of North America’s Great Basin region (most of Utah and parts of Idaho and Nevada). The Great Salt Lake is all that remains of Lake Bonneville. The volcano that produced the pumice is about a mile to the north of the mine. The volcanic ash (pumice) was deposited in the lake, where it was washed and stratified over centuries. The relentless wave process cleaned the pumice of the undesirable heavy minerals that are often found in other pumice deposits.

Pumice is not scoria. Scoria is common lava rock, typically red, red/brown, sometimes black, and is often used as a decorative landscaping ground cover. Scoria forms from basaltic magmas, while pumice is of rhyolitic magma origin. The difference is important. Pumice has many more vesicles—trapped bubbles—than scoria and the walls between them are very thin. Pumice is essentially a foamed glass stone, amorphous (non-crystalline) in structure. The pumice from our deposit is neutral in pH, and more tightly structured (dense) than is typical—it (for the most part) does not float.

DRIED AND PATHOGEN FREE: During processing, our bonsai Eights and Sixteenths grades are heated and dried, eliminating stow-away pathogens.

DRAINAGE: Drainage rates vary by grade: larger grades (stones) drain faster and retain less moisture than smaller grades.

SIFTED AND GRADED: Our bonsai stone grades have been dried and sifted to remove the fines. If water-retentive fines are needed in your soil blend (for a particular wet-loving deciduous tree, for example), blend in a bit of our OneEight+Fines grade.

AERATION: Our bonsai stones are not uniform in shape, and thus provide ample air spaces between particles and amid the natural nooks and crannies found on the surface. The rough-hewn, finely-riven surface of each stone also provides ideal habitat for benefical bacterial and mycorrhizae as well as grippy purchase for mosses or cover mulches.

TEXTURE: The sharp, irregular surface edges of the pumice stone help to promote fine root development and lend to a more healthy tree.

LIGHTWEIGHT YET TOUGH: The weight-savings of our frothy pumice media can be significant, especially in larger pots. Yet our bonsai stone media is tough—resistant to crushing and breakdown, significantly extending the replacement intervals.

PUMICE PURITY:  Our horticultural mine grades are typically comprised of 98% pumice and 2% other igneous minerals, which are not removed through our mining processes.


» Technical Data: the physical and chemical properties of our natural pumice.

» Pumice Safety Data Sheet (PDF)

RŪTSU™ EIGHTS (Pumice Grow Stone)
Naturally pure pumice stone, dried, screened (graded) for Bonsai soil media.
» Size/Grade: 3/8 to 1/8-inch pumice stones (Grade 3/8x8)
Technical Data Sheet (PDF) for Rūtsu Eights™
BUY RŪTSU™ EIGHTS (Pumice Grow Stone)
SHIPPING NOTE: We ship most anywhere. The shopping cart system is set up to auto-calculate domestic (U.S.) shipping, but for those ordering from elsewhere, please email us at fc@hesspumice.com and we’ll see what we can do. For large orders, please contact us for a freight rate.
RŪTSU™ SIXTEENTHS (Pumice Grow Stone)
Naturally pure pumice stone, dried and screened (graded) for Bonsai soil media; seed and cutting propagation media.
» Size/Grade: 3/16 to 1/16-inch pumice stones (Grade 8/12B)
Technical Data Sheet (PDF) for Rūtsu Sixteenths™
RŪTSU™ FINES (Pumice Grow Stone)
Naturally pure pumice stone, top-screened for use in Bonsai soil media blends. Provides inorganic, water-retentive fines for adjusting media drainage rates.
» Size/Grade: 1/8-inch stones to powdery fines (Grade 1/8Fines)
Technical Data Sheet (PDF) for Rūtsu Fines™
BUY RŪTSU™ FINES (Pumice Grow Stone)
SHIPPING NOTE: We ship most anywhere. The shopping cart system is set up to auto-calculate domestic (U.S.) shipping, but for those ordering from elsewhere, please email us at fc@hesspumice.com and we’ll see what we can do. For large orders, please contact us for a freight rate.
hess pumice corporate logo


Contact the Pumice Store:

Product and Large Quantities Information: salesteam@hesspumice.com

Fulfillment and Shipping: fc@hesspumice.com