My succulent potting soil mix: 2022 update

In October 2011, I described a simple recipe for a fast-draining succulent soil mix (here). It remains one my most frequently viewed posts of all times. After almost 11 years, I think it’s time to revisit this topic. Based on the number of questions I get, it’s as relevant now as it was then.

Go to any garden center or nursery, and the selection of bagged soil mixes is staggering. They range from general-purpose formulations to mixes for flowering plants and vegetables to blends for acid soil-loving plants—and everything in between. Typically, you’ll also find at least one mix specifically for cacti and succulents. Sometimes the product has a more fanciful name, like “Palm, Cactus & Citrus” (Kellogg Garden), “Cactus, Palm & Citrus Soil” (Miracle-Gro), or similar.

Dudleyas in my custom succulent soil, planted in Susan Aach pots

In my experience, most commercial succulent mixes contain too much organic material, which keeps the soil too wet for too long. That could lead to rot, especially in cooler weather. The culprit is usually peat. Aside from the vital importance of peatlands as carbon sinks and the environmental damage caused by the industrial extraction of peat, it’s a material that’s unsuitable for succulent mixes: It’s difficult to rewet when dry, and after its has been rewetted, it holds too much moisture, starving roots of vital oxygen. My recommendation: Always read the label and stay away from soil mixes that contain peat, unless it’s just a trace amount (i.e. peat is one of the last ingredients listed).

Fortunately, it’s fast and easy to make your own mix for potted cacti and succulents. It doesn’t have to be as involved as some recipes you find online, but if you want involved, indulge yourself and your scientific mind. And wear a white lab coat if that makes you happy (I’ve always wanted to own one but never have).

My succulent soil mix uses only four ingredients (parts are by volume, not weight):

• 1 part coconut coir
• 1 part commercial potting or gardening soil. Get the cheapest you can find; typically it’s composted forest products and maybe a bit of manure. 1 cubic foot bag is less than $3.
• 2 parts pumice
• Balanced slow-release fertilizer like Osmocote Smart-Release Plant Food

My succulent mix has several basic but vital benefits:

• It allows water to drain quickly, yet it retains enough to keep plants hydrated for a week or two.
• It allows plenty of oxygen in the root zone. Succulents die because water displaces oxygen around the roots.
• It provides enough nutrients without but doesn't weigh the mix down with too much organic matter.

Let’s take a closer look at the ingredients:

Coconut coir is the coarse fiber from the outer husk of coconuts (check out this older post about coir). I like coir because it loosens up the mix while adding a bit of water retention. In contrast to peat, coir rewets fairly easily and doesn’t compress as readily.

Coir is available online in compressed blocks like this. Costco recently had compressed coir at a great price so check if you’re member.

Compressed coir needs to be rehydrated before you can use it. I simply put a block (see below for an example) in a Tubtrug filled with water, top it with a few rocks to keep it submerged, and let it sit for a couple of days. The instructions may say a few hours, but in my experience that’s not long enough for compressed coir blocks to completely rehydrate.

Compressed coconut coir block

Rehydrated coir

The rehydrated coir goes in our garden cart:

To the coir I add the same amount of potting soil (by volume, not weight):

As I mentioned, I use cheap potting/garden/top soil, typically made up of composted forest products

Then I add the ingredient that makes up 50% of my mix: pumice. Pumice is lightweight volcanic rock that, for horticultural use, is crushed or ground into small particles. Pumice is primarily available in the western U.S. In some locations, it’s sold bagged or sometimes in bulk in garden centers or rock yards. Expect to pay $15-20 for a 40-pound bag.

The pumice I currently use is ⅛", perfect for potted plants. A coarser size would be good for landscaping projects.

If you can’t find pumice in a garden center or rock yard, check local feed stores. They may carry a product called Dry Stall. It’s sold as horse bedding material, but is 100% pumice. A 40-pound bag is between $15 and $20. Be sure to get Dry Stall, not Stall DRY; the names are similar, but Stall DRY is a barn deodorizer that’s completely unsuitable for our purposes.

Note for folks in the Davis area: Higby's Country Feed in Dixon carries Dry Stall for $16.99 per 40-pound bag. 

Pumice sold in feed stores under the brand name Dry Stall

Pumice added to coir and potting soil…

…and mixed in

The end result is a loose, airy mix that drains quickly and allows a lot of oxygen to reach the roots

If you can’t find pumice, there are a number of substitutes that can be used. In order of (rough) suitability:

• Scoria (small, crushed lava rock; ¼" or ⁵⁄₁₆")
• Calcined clay (like Turface MVP, sold as athletic field conditioner)
• Gravel (the smallest size you can find, ¼" works)
• Decomposed granite
• Coarse diatomaceous earth (be sure to follow all precautions, such as wearing a respirator)
• Perlite or vermiculite (both are sold just about anywhere although finding larger, economically priced bags may not always be easy; check larger nurseries—they may sell you perlite or vermiculite at cost)

You can vary the amount of top soil, coir, and pumice to create a mix that drains even faster (for example, for extremely xeric cacti) or that holds water longer (for example, for plants from humid environments that like more moisture).

To the top soil, coir and pumice mixture, I add some balanced slow-release fertilizer. For a wheelbarrow of succulent mix as pictured in the photos above, I add an 8-pound bag of something like Osmocote Smart-Release Plant Food. If you make up a smaller amount of succulent mix, just toss in a few handfuls; the amount isn’t critical since succulents are light feeders. You can skip this step entirely if you routinely use liquid fertilizer.

Kellogg's Palm, Citrus & Cactus Mix is only commercially available mix I use

There's only one premade mix I recommend, but it's a good one: Kellogg's Palm, Cactus & Citrus Mix. It contains recycled forest products (finely ground wood from timber industry leftovers), pumice, sand, aged arbor fines (finely ground tree trimmings), dehydrated chicken manure, and hydrolized feather meal (crushed, boiled chicken feathers; another source of nitrogen). In the Sacramento area, it's widely available at Lowe's and Home Depot stores. 

When I'm in a hurry or not in a mixing mood, I simply take Kellogg's Palm, Cactus & Citrus Mix and mix it 2:1 with pumice.

Finally a reality check: As you buy the ingredients for you custom succulent mix, you’ll realize that this isn’t a cheap proposition. You may end up paying twice as much as you would for premade commercial succulent soil. I could argue that the fun of making your own mix is priceless (yeah, and unicorns really do fart out rainbows). Seriously, though, this mix will last a lot longer than any commercial mix. Have you ever wondered where the soil in pot goes? The organic matter gets used up and disappears. Not so with this mix because it contains comparatively little organic matter. You can reuse it time and time again as you repot plants. So yes, the up-front costs are higher, but you’ll save in the long run.

© Gerhard Bock, 2022. All rights reserved. To receive all new posts by email, please subscribe here.