Egmont Pumice Propmix in the coarse grade in a 5 litre size. The perfect additive to make a mix more free-draining, keep soil loose and airy, and add weight to pots that tip-over or are shallow. Egmont Pumice also comes in fine (you can compare the two in the photos) however I no longer stock the fine as everyone only wanted the coarse.

What are the benefits of pumice?

Pumice is entirely natural, volcanic rock, ready to use straight from the earth. Because it keeps its shape even when soaked in water, adding pumice to your mix keeps soil loose and stops soil compacting. 

It adds aeration and improves drainage in any soil mix, and keeps water moving through to prevent substrate (and your plants) becoming waterlogged, reducing the risk of root rot. Although it's a type of rock, it can hold water thanks to being naturally porous. It holds water roughly twice as long as bark, and releases moisture slowly and steadily for roots. 

Pumice is heavier than other substrates used for the same purpose (like perlite), so you won't get a white soil surface over time (as perlite has a habit of floating to the surface when you water), and won't lose it over the edge when you water.

How much pumice should I use?

Pumice is a great soil amendment added to make your own custom soil mix, or can be used by itself. It is added to increase drainage, add aeration, and prevent soil compacting when wet. 

You'll see a difference by adding as little as 10% pumice to your indoor plant soil mix. For succulents up to 50% pumice and half potting soil is popular. Cacti and euphorbia increase to around 60% pumice and 40% potting soil. A trick for cuttings that easily rot is to start them off in 100% pumice. Remember to fertilise as pumice doesn't provide all the essential nutrients plants need.

How does pumice compare to perlite and vermiculite?

Pumice is heavier than both perlite and vermiculite, so won't float to the surface of the soil when you water. I'd put it on par with perlite for water-sensitive plants (like succulents or cacti). It doesn't retain or hold as much water as vermiculite. It also won't decompose like other ingredients added for drainage (like coir and rice hulls).