Best Potting Mix for Succulents and Cacti: How to Choose

The Short Answer

The best potting mix for succulents and cacti is a free-draining blend in which about half the volume is coarse sand, perlite or pumice and the rest is ordinary potting soil. A bagged cactus and succulent mix does the job, and so does a homemade one. University of Illinois Extension gives the simplest version: 1 part potting mix and 1 part perlite, or 1 part coarse sand and 1 part potting mix.

The reason is rot. Clemson’s fact sheet on indoor cacti states that waterlogged soil will quickly lead to rotting of the roots, and University of California guidance for succulents says roots must never be exposed to standing water. University of Illinois Extension adds that these plants do not appreciate a constantly moist medium, which is what regular potting soil on its own tends to give them. When rot has already started, the root rot recovery guide covers the rescue.

What a Succulent Mix Has to Do

A good mix lets water run through and leaves air around the roots. University of Georgia Extension explains the stakes for any houseplant: applying too much water can suffocate plant roots. Coarse particles keep open spaces in the pot, so the mix drains and dries between waterings.

Drainage does not mean poor soil. Clemson points out that cactus plants prefer a rich soil as long as it is free-draining. That is why every university recipe below keeps potting soil, loam or peat in the blend and adds grit to it. A pot of pure sand or gravel is not what these sources recommend.

Three drainage ingredients appear again and again in extension recipes:

• Coarse sand. Mississippi State specifies coarse, clean sand, and Clemson asks for very coarse sand or grit.
• Perlite, which appears in the California, Illinois, Mississippi State and Georgia recipes. Our comparison of perlite and vermiculite explains why perlite is the one used for drainage.
• Pumice or small lava rock, which the University of California recipe uses alongside perlite.

Five University Recipes Compared

Extension services do not agree on one formula, which is useful to know. It means the plant tolerates a range and you can work with what you have.

Source	Recipe by volume	Sand, perlite and pumice share
University of California	Equal parts potting soil, coarse sand, perlite, and pumice or small lava rock	75 percent
University of Illinois	1 part potting mix to 1 part perlite, or 1 part potting mix to 1 part coarse sand	50 percent
Clemson	Equal volumes of peat-based potting soil and very coarse sand or grit	50 percent
Mississippi State	1 measure potting soil, 1/2 measure coarse organic material, 1/2 measure perlite, 1 measure coarse clean sand	50 percent
University of Georgia	2 parts garden loam or potting soil, 2 parts sand, 2 parts peat, 1 part perlite	43 percent

The last column is simple arithmetic on each recipe. Georgia’s mix has 3 parts of sand and perlite out of 7, which is 43 percent. California’s has 3 gritty parts out of 4, which is 75 percent. The other three come to half.

Mississippi State’s sheet shows how a cactus mix differs from a general one. Its standard indoor mix uses 1 measure each of potting soil, coarse organic material, perlite and sand. The cactus and succulent version keeps the soil and sand and cuts the organic material and the perlite to 1/2 measure each, so the blend holds less water.

Buying a Bagged Mix

A commercial cactus or succulent mix is an accepted choice. University of California and Clemson both list it ahead of their homemade recipes. Bags vary, though, so judge one against the recipes above. Open it and look. If you see little sand, perlite or pumice and mostly dark, fibrous peat, treat the bag as potting soil and cut it 1 to 1 with perlite or coarse sand, which turns it into the Illinois recipe.

Rain forest cacti are the exception to the gritty rule. Thanksgiving, Christmas and Easter cacti come from humid forest conditions, and Clemson says this group requires more organic matter in its soil than desert cacti do. Its mix for them is two parts peat moss, one part garden soil and one part sand.

Skip the Gravel Layer

Putting gravel in the bottom of the pot is a common piece of advice for succulents, and it works against you. University of Illinois Extension calls it a myth that a layer of gravel beneath the soil improves container drainage. Water does not pass straight into the gravel. It gathers in the soil just above the layer until no air space is left.

University of Missouri describes the same effect as a perched water table. A coarse layer at the bottom shortens the column of potting mix, and drainage is reduced. In a shallow succulent bowl, that puts the wettest zone right at the roots. University of California gives the same instruction for succulents: avoid placing rocks in the bottoms of pots. Fill the whole pot with the same mix. The physics is laid out in rocks in the bottom of a pot.

What does matter is a hole. Illinois describes a drainage hole in the bottom of the container as critical, because it lets water drain freely so air is available to the roots. University of California likewise says to choose a container with drainage holes to prevent standing water.

Match the Mix to the Pot

Pot material changes how long any mix stays wet. Mississippi State notes that clay pots are porous and let moisture evaporate through the sides, so the soil dries faster, while plastic and glazed containers hold moisture longer. University of Georgia adds that the slower evaporation from plastic raises the danger of overwatering. It follows that a plastic or glazed pot is the place for the grittier end of the range, such as the 75 percent California recipe, and that a 50 percent mix has more margin in unglazed terra cotta. For more on the trade-off, see terracotta versus plastic pots for houseplants.

Size matters as well. University of California suggests a container at least 4 inches in diameter for most small succulents and at least 6 inches for larger ones. When repotting, go up only a little. Illinois advises a container just 1 to 2 inches larger for rooted cuttings, and Clemson warns that in a pot that is too large the soil may stay moist and lead to rot.

Repotting and Watering in the New Mix

Clemson names April as the best time to repot cacti, just as they begin summer growth, and recommends waiting several days after repotting before watering. Succulents are handled differently in the California guidance, which says to water thoroughly after planting and then let the soil dry out.

After that, the mix tells you when to water. University of California’s cue is to apply water only when the soil is completely dry at least 1 inch below the surface. Push a finger into the pot to check. Clemson treats the seasons separately for cacti. From March to September they are watered like any houseplant that prefers to dry slightly between waterings. During winter dormancy they get just enough to keep from shriveling, usually a light watering every few weeks.

If the mix is still wet an inch down long after watering, the blend is too heavy for your pot and room. Repot into a version with a larger share of perlite, pumice or coarse sand.