Soil, dirt, earth; what we chose to grow our collection in will contribute to its overall success. The final product, however we combine it, is referred to as our growing medium. Here is the important part that is often not discussed: what will work best for your succulent collection depends completely on your growing environment.
I preface all of my advice with the following: I am not a botanist nor a horticulturalist. My formal education consists of graphic design and photography. What I am is an avid, experienced succulent collector who is enthusiastic about plant care. My goal is to provide advice to the four season succulent gardeners, those of us who can not grow outside year round.
Often times, we see photos of succulents growing on-line in their natural habitat, in what can only be described as impossible conditions. The side of a cliff, middle of a desert, poking up through a pile of rocks. And they are thriving- how is that possible? I look sideways at mine and they flop over and die? We need to understand where they come from, and then understand that our domesticated plants will not magically thrive in the same easy going way that naturally free ones do. We have taken them, bred them, hybridized them & babied them.
When potting indoors, the first step is choosing a medium that will keep our beautiful collections happy and thriving.
Commercially sold, generic 'cactus soil' come with a variety of claims at a variety of prices. For those of us who would rather spend our money buying more succulents and cute pots, forking over big moolah for dirt can seem annoying. But choosing the right medium will be one of the top deciding factors of whether your succulent thrives or dies. What you are looking for is something that does not hold moisture. For the majority of use four season growers who deal with extreme humidity and forced air inside over winter, a medium with much more grit will be necessary.
Examples* of grit would include a combination of the following:
-fine gravel, rinsed
-chicken grit (crushed granite)
-coarse sand
-pumice
-lava rock
-perlite
-leca
-akadama
* there are many more that could work- think inorganic additives that won't hold moisture.
These options vary in price and availability. When mixing your own, you want to be able to take a handful of wet mix and squeeze it in your hand. If it doesn't crumble when you release your hand you need to add more grit.
I'm sure you were hoping to read this blog and find a recipe for the perfect mix and call it a day. The truth is I would be doing you and your collection a major disservice if I said: use this with this and your succulents will thrive.
I will however tell you what works for me and my growing environment and it will be a good starting point for you. For my indoor potted succulents I use a 50/50 organic to grit ratio (40/60 for some I know to be prone to rotting more easily). I bottom water my mature, larger succulents and not often; approximately every 4-8 weeks. I start with cactus soil and worm castings as my organic matter. I add perlite and chicken grit (crushed granite), and sometimes leca (clay balls) & lava rocks when my budget allows.
For starters and leaf props I use a similar mix with slightly more organic matter and none of the large, chunkier grit. I like my props more on the organic side as they need to be watered more often. Remember the smaller the succulent, the less water they can store, the more often they will need watering.
Late spring, summer and early fall here in Canada, my succulents grow outside. The medium for outdoors over summer is much easier and more forgiving. They can and will flourish in nearly anything I have handy as long as the pot has drainage and they are protected from any cold dips in temperature.
For your indoor succulent collection, try mixing your own medium. Once you have done the squeeze test, fill a couple of pots, (what you typically use, whether it be terra cotta, ceramic or plastic) place them where you grow your plants and water as you normally would. By the next day is it nearly dry? By day two is it fully dry? If so then you are good to plant. If not, add in more grit (inorganic matter) and try again. Also note: you can, and should, add fans. Fans will help your pots dry out and good airflow is essential to growing strong, healthy succulents.
To recap; for your potted indoor succulents, you need a medium that is less organic than commercially sold 'cactus soil' to dry quickIy. Your succulents don't know when to stop taking up water. If your medium stays wet this could lead to bursting or rot. Outside, with the bright sun and natural wind this is less of an issue. Inside, we need to do all we can to ensure they thrive in our household environment. Watering lightly is not the solution; it will result in shallow roots and stunted growth. They want to be watered deeply & dry quickly.
I hope this has guided you down the succulent success path to mix your own, well-draining medium, ensuring your collection stays happy and healthy!