What is substrate? What soil is best for potted succulents?
Google definition: Substrate - the surface or material on or from which an organism lives, grows, or obtains its nourishment.
One of the most frequent questions we are asked, “What is the best potting mix for my succulents?”. And it's a brilliant question! Back in our 101 intro page, we've established that succulents need a well-draining, impeccably aerated, and fast-drying potting mix. But remember, there also has to be enough moisture left behind for the roots to take a drink after watering. The mix cannot be too dry that no moisture is retained.
While most succulents are adaptable to a range of soil conditions, some others require very specific care. That means that the best mix is going to depend on your environment and the plants you wish to grow. While we can’t tell you exactly what’s going to work in your unique situation, we can share some tools to help you figure it out. It's best to figure out your hardiness zone to help you understand your environment and how your plants will grow and adapt.
Soil And Your Environment
How does your environment play a role in your mix and how do you know which is the right soil mix for your environment? Humidity, temperature, light exposure, and the weather all affect what type of potting mix will be best for your plants.
Over-watering, rot, and fungal infections are common in most humid and rainy places. Gritty, highly inorganic substrates with a lower moisture retention capacity will be advantageous and assist in reducing these issues in these kinds of environments.
Whereas in very hot and dry climates, the same plants may struggle to stay hydrated in a substrate without enough organic material to retain moisture.
Succulents that are grown indoors for at least part of the year and in cold regions may experience a combination of these two factors.
Need to find your hardiness zone? Live in the USA, click here.
Organic & Inorganic - What Do These Mean?
When creating a potting mix for succulents, there are two main components to think about: organic and inorganic materials.
Organic materials come from living organisms, and they break down over time through the process of decomposition. Organic materials can be further put into two categories.
The chunky ones, like bark.
And ones that are dirt-like and retain more moisture, like coco coir, compost, or peat moss.
Note: These dirt-like components may be used a little or a lot, and are sometimes referred to as “wetting agents” since they retain more moisture. Not all pre-made potting mixes will contain these finer materials. Mixes with low or no fine material are often referred to as “gritty mixes”, like Bonsai Jack soil mix.
Inorganic materials are things like minerals and rocks. Unlike organic materials, inorganic ones do not break down (although they can sometimes be crushed or erode over time, this will be very slow).
Note: Particle sizes should be roughly between 1/8-1/4” or about 3-7mm.
→ Our Tip: Never use fine, beach, or play sand in your succulent mix, it is far too dense and airless and will not improve your drainage.
→ Pro Tip: Large rocks at the bottom of the pot won't help either! With perched water in the soil, it remains wet for an extended period, you run the risk of causing rot.
Creating Your Potting Mix:
Ingredient Examples:
Organic
Pine Bark also called Pine Fines
Potting Soil | (this can be a succulent-specific mix or a general potting mix)
Inorganic
Calcined or Fired Clays (such as LECA, Turface, or Monto)
Note: Although charcoal is wood and therefore organic, it is more similar in property to the other inorganic materials, so we include it here.
Chicken Grit (crushed granite)
Scoria aka Lava Rock
Many other usable substrate options are not listed above. Just make sure they are not detrimental to your plant's health.
Succulent Soil Mix Examples:
So, what combo of inorganic and organic materials is best? A 50/50 ratio is a great starting point. Then, as you discover what works best for you, make the necessary adjustments based on your best judgment, the succulent species, your surroundings, and the particular combination of ingredients you've selected; it's all part of the learning process, and we learn best from making mistakes!
50% regular potting soil + 50% perlite, chicken grit, scoria, etc
The basic potting mix is affordable and easy, but depending on the potting mix chosen, it can be too dense if enough grit is not added. To combat this, try to choose airier potting mixes with larger particle sizes (for example those made with coco coir rather than peat moss) and increase the inorganic content in regions that experience cold winters and above-average humidity.
Even potting mixes formulated for succulents will benefit from additional grit to improve drainage and airflow. *Especially those mixes made with peat moss.
This brand sells premium potting mixes and individual components that can be used as is, combined, or modified to meet a wide range of needs. *Bonsai Jack is not affiliated with Succulents and Propagation, we just like their products.*
111 General Succulent Mix: This coarse, gritty mix is PH balanced and can be ideal for many species, indoor growing environments, and humid regions.
Coarse material sizes allow air and water to pass through freely while clay products absorb water and release it slowly to plants as they need it.
Pine coir balances PH and provides organic content.
11011 Inorganic Mix: This mix is 100% inorganic and best for plants like Lithops that prefer little to no organic content. This mix would also make a good base to start your potting recipe with, add in organic components as needed to achieve the desired amount of moisture retention.
50% pumice, 25% pine bark chips, 25% coco coir
Pine bark increases space for air pockets and drainage.
Pine bark has an optimized PH content
Coco Coir holds a ton of moisture. Beware if you live in wet/humid conditions.
Becca's Succulent Soil Mix
4 Parts
2 Parts or 50% | Hoffmans Organic Soil
1 Part or 25% | Organic Perlite
1 Part or 25% | Bonsai Jacks 111 mix
There are countless options & substrate combinations to choose from for your plants. You can pick just one ingredient from each category or mix a whole bunch! Don’t stress about this decision. It's all trial and error. Over time, you will make adjustments and your mix will continue to improve until you find exactly what works for you, and depending on which plants you collect, it may vary vastly between them. Keep in mind some different species require completely different soil (like Lithops, Sansevieria, and many others).
Need further assistance?
If you are ever unsure about your exact soil needs, post your questions in the Succulent & Propagation group on Facebook and connect with fellow local members. You may also ask your local gardeners. They tend to have the most accurate advice—advice that is specific to your climate. By talking to those in the same hardiness zone as you, and experts alike, you can start to build on that knowledge!