Best Potting Mix for Succulents?

[izzibusybee]

In that case I’d add sharp sand as well as perlite and maybe pick out some of the ‘lumpy bits’ so it’s lighter. John Innes is just like standard potting soil that’s been sifted, and it feels a little sandy so they probably add some.

[Leafmite]

This is a timely thread for me. I have not had much luck with succulents so, when I fell in love with a String of Pearls this spring, I stuck it in the Neem tree's pot and, so far, it is thriving. I just made a few starts of it so I will try it in one of the proposed mixes as I really want one to hang in my kitchen window. I am going to look for a shallow hanging basket, I think. Thank you for everyone who contributed!

[estación seca]

There is no one good potting mix for all succulents, any more than there is one good potting mix for all orchids. People need to take into account the needs of the individual plant. There are thousands of different kinds of succulents scattered among hundreds of plant families, coming from all over the globe.

I believe received wisdom about succulent potting mix is the main reason people think succulents are hard to grow. Adding sand to potting soil mixes usually results in very heavy, airless, water-retentive mixes that are not good for most succulents. Commercial bagged potting mixes usually contain perlite, sand, and sawdust or milled peat. Neither is this is a good mix long-term. Plants in such mixes must be repotted every 2 years as the peat or sawdust breaks down to something anaerobic. Cacti especially struggle in peat or sawdust based potting mixes.

The string of pearls plant (Senecio rowleyanus) is picky about having lots of air at the very shallow roots, and cool to intermediate temperatures all year. It is difficult to grow for most people because their temperatures are too high, or they use a heavy potting mix. The plant normally grows in small pockets of loose organic matter on rocks or places where leaf litter accumulates on the ground. I have seen it grown successfully in very loose mixes of mostly perlite with a touch of milled peat, and also in small pumice. In a too-dense potting mix it dies quickly when temperatures rise, or the gardener overwaters.

Many specialist succulent nurseries in the western US grow their plants in nearly pure pumice of different sizes. They may add up to 10% of some kind of organic matter, but often they don't. This works well for most succulents other than the very small ones. But pumice is hard to get outside volcanic zones.

Leafmite, since pumice is difficult to obtain in the midwest, consider using small pieces and dust of volcanic cinders for your succulents. Add perhaps 10% potting soil if you think your medium is not water-retentive enough, but I don't think this will be the case. For the Senecio rowleyanus, fill most of the pot with small cinders, and top with an inch of fine potting soil. The plant will have moist roots with air beneath.

[Arizona Jeanie]

Thanks to all for the replies. ES, is "large particle perlite" different from the usual stuff sold by the bag at the big box stores?
Also, if using perlite or pumice, how do you keep it from floating out of the pot when you water? Aren't they both light enough to float? That's why I was wondering about pea gravel--it's a lot cheaper also.
Also, one of the Epi's is of the really large kind, with 4-6 ft stems--I'm volunteering at the greenhouse where it grows. I don't know how it got there, but it looks in need of re-potting. Same mix as for the smaller epis, same small pot?
I recognize that different succulents will do better in different mixes. What do you recommend for the larger Crassula? (Jade plant and silver dollar jade, 3-4 ft tall with old woody stem in a pot.)
Thanks, I appreciate your expertise.

[Leafmite]

Hey, thanks! That is quite interesting about how these grow and the troubles with sand. My mixes rely heavily upon perlite due to the cool conditions in the winter but I do sometimes also add some sand, depending on what I am growing.
Thanks for giving me some guidelines for the string of pearls. I will need to look around and see what I can find.

[estación seca]

Originally Posted by Arizona Jeanie

...is "large particle perlite" different from the usual stuff sold by the bag at the big box stores?

Yes, large particle perlite has particles about 1/4" / 7mm diameter. I have seen it sold at nurseries in metro Phoenix. It comes in very large bags from Therm-O-Rock West in Chandler, AZ. Maybe a hydroponics shop or nursery in your area carries it?

Small particle horticultural perlite retains water a very long time when used as a primary constituent of media in larger containers. It is good mixed 95% - 5% with coconut fiber (coir) for succulents in smaller pots, say under 6" / 15cm.

Where you live, similarly-sized pumice might be easier to come by. I use the big particle perlite for larger plants. It makes large cactus or succulent tree pots a lot easier to move around for winter. I would use the small particle stuff on the little things like sedums.

Originally Posted by Arizona Jeanie

Also, if using perlite or pumice, how do you keep it from floating out of the pot when you water? Aren't they both light enough to float? That's why I was wondering about pea gravel--it's a lot cheaper also.

Pea gravel works just fine but it weighs a lot more. Perlite will float out, but pumice doesn't. Pumice is easy to splash out with a stream of water, though. You have to be careful and pay attention when you water. Commercial succulent growers use a fine water wand so they don't dislodge the perlite.

Originally Posted by Arizona Jeanie

Also, one of the Epi's is of the really large kind, with 4-6 ft stems... it looks in need of re-potting. Same mix as for the smaller epis, same small pot?

Good chance it's Epiphyllum oxypetalum, with white night-fragrant flowers. All the Epis are epiphytes or lithophytes in habitat, so they need very well aerated soil. Use the same mix for the big one. I would use the smallest pot the current root system fits into after you shake off all the old mix. If it hasn't been repotted in years, there's a good chance the mix is rotten muck, and the plant will have a much smaller root system than you might think. Epis can get this big in a 1 gallon can, but they can be top heavy. What you don't want is a large pot full of medium that is so dense it can never dry and never gets air to the roots.

Originally Posted by Arizona Jeanie

...What do you recommend for the larger Crassula? (Jade plant and silver dollar jade, 3-4 ft tall with old woody stem in a pot.)

You need to repot succulents every 2-3 years if you use a mix with a lot of organic content. That's a lot of work for a huge plant. I don't want to bother with that; I only want to repot when they outgrow the pot. So I use soil dug from my garden for most of my cactus and succulents. I screen it with several different things to get different particle size. I usually mix in lots of perlite or pumice to make the pot easier to move for the winter.

A lot of big cactus and succulents do just great with some (or entirely) local heavy clay in the pot. They get minerals from this they can't get from bagged cactus mix. For cactus and big succulents you can use what Steven Hammer calls Mabel mix: local soil plus pumice or perlite, whatever proportion makes the pot easier to lift. For big plants like this I'd use 75%-90% pumice or large-particle perlite mixed with local clay or sandy soil, unless the plant is never moved.

Originally Posted by Arizona Jeanie

Thanks!

You're welcome.

[Arizona Jeanie]

Wow, Estacion, thanks for all the information, it's taking me awhile to digest! I'm going to look for appropriate products. I don't think there's pumice available here, but I did find some on-line. May be some available in Flagstaff, I'll have to check. That's where the cinders used on our roads when it snows come from. Maybe I can just sweep up a few of those next Winter, if we ever get any snow again.
My yard has almost no topsoil, maybe an inch, and I guard it carefully and don't dig it out. I do like the soil idea though, I think I can buy a bag of decent topsoil at the local landscape materials place. They normally sell it by the ton, but will let me buy a birdseed bag full for a few bucks if I visit the yard.
I've tried something called "gritty mix", a small Echinopsis hybrid is doing great in it, but the sedums dried out too fast.
I'll try for a visit to the Phoenix area in December, when the aloes are blooming at Desert Botanical Garden. I can look for the large pumice (vermiculite?) from Thermo-rock then.
Speaking of Aloes--I don't have any now but would like to add a small one. What do you recommend for potting those?
Thank you again and some more for the good advice, you're a great resource.

[estación seca]

Small pieces of cinder work as well as pumice.

Thermo-Rock is wholesale only, but I've written them asking who carries their products. Baker Nursery, where I used to purchase it, closed, and a housing development sits there now. I'm happy for the daughters of the late founder, but miss the nursery.

The great majority of aloes are easy, vigorous plants that will grow in any potting medium whatsoever. A lot of people use 50% potting soil and 50% pumice, perlite or cinders. The Huntington Gardens in Los Angeles sells Aloe hybrids by Karen Zimmerman. She aims for small windowsill plants with beautiful leaf coloring and texture.
>> Fantasy Aloe Hybrids

[Arizona Jeanie]

Those Aloes are wonderful! I think I've seen some of them in with the plants from Altman's that show up at our local home depot. I'll be keeping an eye out for one I like, or maybe wait until I get to the DBG gift shop.

[estación seca]

Tucson is another hour and a half from Phoenix, but consider going to Living Stones / Plants for the Southwest. They also mail order.