Using the word “brilliant” to describe pumice might lend to people thinking it is a shiny rock. Those of you who have ever seen or touched pumice know it is anything but shiny. But what I am meaning is that I find pumice impressively brilliant, or in other words, “smart” as a soil amendment. As a kid growing up in Oregon, pumice was talked about as an interesting rock because it is so light weight. In fact pumice will float in water for a while because it has so many holes in it.
- Pumice is great for improving drainage in soil.
- Pumice aerates the soil.
- Pumice naturally retains soil moisture.
I think I’ve lost more plants because of poor soil drainage, both indoors and outdoors, than any other reason. Only after I started doing soil testing, planting the same plant in different soils, that I realized it was the soil and not me that was the problem. Some plants don’t tolerate being too wet, and most plant roots will eventually rot if there isn’t good enough drainage in the soil. Adding small pieces of pumice to soil creates space and thus allows for better drainage of moisture
Related to this is aeration of the soil. Allowing air into the soil is healthy for plants. Plant roots like to breathe. Helpful organisms, like fungi and bacteria in the soil, also need air. Pumice is full of holes and those holes are full of air.
Finally, due to its porous nature, pumice lends itself to keeping the soil moist longer than if it weren’t there. This is amazing to me that pumice simultaneously improves soil drainage and moisture retention. It’s easy to work with and pretty hard to go wrong.
In some areas of the country it is more difficult to find pumice. If you are looking for pumice, Green Planet Naturals has made it available for sale here.