A Few Notes on Pumice

Before I go collecting, one task at hand is making sure I have enough clean pumice for my newly collected trees. From my experience 100% pumice has produced very good results, growing strong and healthy new roots by providing just the right amount of water and air to the tree's root system.  In addition to using 100% pumice for collected material, I also use pumice as one of my main soil ingredients for all trees and as a drainage layer at the bottom of every pot. As you can probably imagine this is why I use lots of pumice and buy it in bulk to cut down on costs.

Sifted and washed pumice


So far I have purchased pumice from two locations in California .  If you know of any other locations, I'd love to hear where in the comments section below. For reference 1 yard is about the amount that would fill the bed of my Toyota Tacoma. The two locations I know of where you can purchase pumice are:

Air Vol Block-

$105/yard, $7/bucket or $4.99/50 pound bag


1 Suburban Rd.

San Luis Obispo, CA 93401


American Soil and Stone-


Call this number first: 510-292-3000

Then pick it up here:

689 Bancroft

Berkeley, CA


When buying directly from the locations above, the pumice will be very dusty and dirty with many fine sized particles that stick to the larger pieces.

Pumice in it's raw state, purchased from Air Vol Block


The containers and boxes we put our trees in are relatively small and confined environments.  Which is why I believe we should be providing the trees root system with the best possible growing medium.    Here’s a picture of the reason I sift and rinse all the fines out of the pumice. While this might be an extreme case the fines can clog drainage holes, block air/ water from roots and make it difficult for new roots to make use of the entire pot.

A lot of pumice dust after getting wet and drying


It sure would be nice if someone offered clean pumice in different sizes for a reasonable price. Sifting and rinsing large amounts can be a challenging and time consuming task. I especially dislike the amount of dust that’s produced and make every attempt not to breathe it in. I’ve changed the way I rinse and sift pumice a few times now and I’m sure I’ll do it again to make the process more efficient. Most recently I’ve been doing the rinsing over my lawn and using Anderson flats to hold and dry everything. Anderson flats are great because they are inexpensive and work well for newly collected material. I use a staple gun to add screen mesh to the bottoms. If interested, I purchase mine here:  https://www.stuewe.com/products/anderson.php


The way I currently do it is by rinsing.


Sifting to appropriate sizes.


Then rinsing again until the run off water is clear.


And finally leaving it in a sunny area to dry.  Using bone dry soil is always a smart idea because it helps to get rid of air pockets inside our Bonsai containers.


Bonus points if you can tell me the name of the plant in my header at the top of the site and where it grows?

Below is a little spring orchid I have growing under one of my benches-a native CA orchid.  Thank you very much for reading!





5 thoughts on “A Few Notes on Pumice”

  1. I just discovered you from Wayne at Stone Lantern. Great info on pumice. The picture up top, is it a succulent? Echeveria? Lovely orchid.

    1. Thank you Mark and Deborah for the comments! Very good guess Deborah, it is a succulent but not Echeveria. Thanks!

  2. I have been washing my pumice also. I wash it in a tub of water sifting it through the screen as if it was dry. It rinses clean quickly and the dust settles to the bottom of the tub. It then goes into those woven poly bags used for sand bags. Water drains right out and after a few days in the sun the whole bag is dry. You can then sift for size later without any dust at all.

    1. Nice, glad you are washing it. I like your ideas and will try. So what do you do with all the white/grey gunk water?

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