Horticultural pumice, 1/4–1/2"

Each bag contains 3 dry quarts of coarse-grain pumice. The typical piece size is around 1/4" with chunks up to 1/2". The pumice has been sorted to remove foreign materials and reduce fines.

⚠️ **FINES (small pumice particles) easily become airborne and are hazardous to inhale. It is recommended to wear a mask and dampen pumice when using it to reduce risk. Getting pumice wet will also make it easier to mix into your soil—it has a tendency to bounce to the top because it is lightweight!**

Horticultural pumice is finely crumbled volcanic rock that is extra light because it formed from lava foam, full of small bubble-holes. Pumice is key to mixing a well-draining soil for cacti and succulents. There literally is no such thing as "too much pumice" because a lot of plants are happy to grow in a 100% pumice soil as long as they are given supplemental nutrients... it's actually a common method for rooting cuttings.

My torch cacti enjoy a soil that is about 50-50 pumice mixed with organic soil. For many cacti and succulents, inorganic soils like pumice mixed with small stones and other lava rocks more closely mimic the low-nutrient growing conditions they are accustomed to in nature. The porosity of pumice rock helps keep soil ultra lightweight, so roots stay airy and dry. At the same time the porosity retains moisture well. When used liberally in soil, water drains immediately but light moisture remains available to the plant in the pumice, so it is much more difficult to lose a plant to the soggy conditions that cause root rot.

Alternatively, pumice makes a decorative light colored and lightweight top-dressing that helps hold moisture in the soil (though I find it can discolor over time and repeated waterings).

How much do I need? 1 dry qt is the plastic container shown, equal to about 0.9 lb of pumice; 3qt fills most of a 6" cubic box.