Soil and drainage

by Rosario Douglas

A common mistake that succulent plant growers new to the hobby make is to use the wrong type of soil.   This is understandable because we all are familiar with the dark, nutrient rich, water retaining soil that is recommended for vegetables (tomatoes etc.) or ornamentals like roses.

Succulent plants are different and the name “succulent” gives us a clue since this refers to their ability to retain water.  Succulents have evolved a variety of strategies (succulence, CAM metabolism etc.)  that allow them to survive in dry and often hot climates.   A tomato plant requires water at regular intervals or it will wilt and die very fast but succulents, on the other hand, can survive and look good much longer with little water.

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Copiapoa cinerea grows along the coast in central Chile, a very dry place.  Notice the rocky soil.  Placing this cactus on rich, water-retaining soil would mean certain death by rotting.   Photo by Mike Douglas.

Succulent plants are found in many habitats, but they all have something in common – well-drained soils.   The degree of drainage varies depending on the succulent. For example, cacti tend to require less water and often grow in loose, rocky soils or even rock cracks. Regardless of the type of succulent, good drainage is essential to the well-being of any succulent plant.

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Euphorbia canariensis, a succulent from the Canary Islands, growing out of the rocks.  There is certainly some soil where the roots are, but like this plant, many other succulents can grow with small amounts of soil.  Photo by Michael Douglas.

As a succulent plant enthusiast you will soon realize that there are many types of succulent plant mixes, some commercial and others in the form of “recipes” that you can mix yourself.   Commercial succulent soil mixes tend to be expensive if you have many plants.  As long as you have local access to the materials you need, it is often more practical and certainly less expensive to make your own succulent plant soil mix.

Your next step will be to find the best “recipe”.  At this point you will notice that succulent plant soil mixes are like BBQ sauce – there are many types.  The only requirement is that any soil mix has to provide GOOD DRAINAGE.   Going online you can find many videos and articles about different mixes and soil ingredients you can use.   Probably the best advice is to try to keep it simple, try to find a place near you where you can get materials in bulk rather than by the bag, read articles about this subject, experiment – and keep notes.

Your mix should have some regular rich soil (no fertilizer added) and materials that allow good drainage.  Succulent plants grow far more slowly than non-succulents and thus require less fertilizer than non-succulent plants.

For the drainage material you can use: perlite, vermiculite, pumice, river sand (washed), small granite chips or limestone chips etc.  The rich part of the mix has to be less than the drainage components.   After some experimenting I have arrived at a mix that works fine for me. It is 1 part rich soil (no fertilizer added), 2 parts river sand and 1 part granite chips. At this point you can add a small amount of fertilizer pellets such as Osmocote.

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Echinocereus reichenbachii ssp. baileyi is an example of a cactus that grows on granite.  Shown here are specimens photographed in the Wichita Mountains National Wildlife Refuge in southwest Oklahoma.   Photo by Michael Douglas

The type of rock you use may vary depending on the succulents you grow.  Some succulents grow naturally in limestone soils while others grow in sandy soils etc.   You might not want to grow a succulent that naturally grows on granite in a soil mix that contains limestone.

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Ariocarpus fissuratus, from southern Texas and Mexico (Chihuahuan desert) is a good example of a cactus that grows on limestone rock.  Photo by Michael Douglas

Arriving at the succulent soil mix that works best for you will take some experimentation and the  availability of local materials will play a role determining the ingredients you use.  Keep good notes and see how your plants respond to the mix you are using.  In the end whatever keeps your succulents happy and healthy and does not break your budget should be the winning succulent plant soil mix for you.