ICSS Stories

Cacti soil and how to choose the best option for your plants

by Jurate Šimkutė | soil | 22 Feb 2022

Arid deserts, scorching sun, sandy rocky terrain that seems to be extremely unforgiving to any sort of life, however, the majority of cacti thrive on these sort of conditions and provide us with beautiful spination and flowers. Every single person will have a different soil mixture however few things will never change: soil must be porous and well draining to ensure that the best results in steady growth, regular flowering and avoidance of diseases are achieved.

A vast variety of organic or inorganic ingredients can be used, however sourcing them here in Ireland might be a difficult task. In this article I will discuss a couple of ingredients for your mixtures that are readily available in the majority of the gardening or DIY stores.

One of the best base organic material that you can get in stores is John Innes no.2 soil, this particular soil contains a higher loam amount with some added grit and peat. PH for this particular soil is 5.5 - 6.0 which is ideal for most of cacti that we grow.

Sand - Best kind of sand used for your plants is sharp sand. Play sand or beach sand should not be used for our plants as it is too fine and beach sand will contain huge amounts of salt that would eventually kill the root system and plant itself.

Grit - wonderful inorganic addition in cacti soil mix as it offers brilliant drainage and opens air pockets around cacti roots so it has more space to grow. It also can be used as a top layer not only it looks tidier but it also reduces the danger of rot around the cacti neck.

Vermiculite - another inorganic addition to the soil mixture. Vermiculite is extremely light and powerful in moisture retention. It is alumino - silicate clay mineral that can potentially absorb up to 4 times of its own volume in water. It also helps soil aeration and drainage.

Perlite - Porous, fine grained material that is of volcanic origin. Provides permeability and low water retention, prevents soil compaction. It is one of the best materials to start your plants from cuttings.

Molar clay - This particular clay is being sold as cat litter or oil absorbent for diesel or petrol spills. Molar clay helps with water and nutrient retention however it is still fast draining. Another useful property of molar clay is that it does not break down easy.

Pumice - has uniform porosity and therefore is highly permeable to air and has high water absorption capacity. Like molar clay it holds onto water and nutrients releasing them at the slow and steady rate. Even in cold weather pumice may hold the moisture up to 48 hours.

So these are the main ingredients for good cacti soil. Only pumice might be harder to come by in Ireland, therefore most of the time we need to import it from countries like Germany, Italy, Poland or Iceland.

Mixing cacti soil
Various ingredients that you would incorporate in your soil mix should be sieved through to make sure that there are not small particles that could potentially cause caking or bad drainage. Mix your ingredients thoroughly by spreading and turning over several times.

For cacti that do not have a large tap root 1:1:1 mixture of John innes no. 2 , grit or molar clay and sharp sand can be used. For cacti genus like Turbinicarpus, Lophophora, Ariocarpus or anything that has large taproot I like to use 100% inorganic mix that consists of 40% pumice, 40 % molar clay or grit and 20% of sand. So far great success has been achieved with these particular mixes that are not too hard to obtain and are readily for sale in the majority of garden centers or DIY shops.

I hope you enjoyed reading about soil ingredients and mixes and please share your best mix on our friendly Facebook group.