I'm writing from New Zealand where I have never heard of the need to use gravel, let alone "a special kind" to grow these plants. I have had half a dozen varieties of these plants in pots for many years growing successfully in a standard free draining potting mix. I shall be interested to hear what others think.
Lizzie B

It helps the leaves to not rot (faster). Of course, sempervivum leaves will always eventually rot, but they rot much faster without a shield to protect them from coming intact with the soil.

I'm no semp expert though, so I'm sure one of the experts on here will answer your question with more detail

Just saw this thread, and it makes sense. I've only have one medium sized bonsai pot with
2 varieties, and am using a course succulent mix. So far (~2yrs) they're doing fine....I keep them
dry, though they're getting rained on lately.
This reminds me to shelter them from too much water.

But I have some course sand I got out in our local desert, where there are many cacti,
and may replace the top 1/4" of succulent mix with the sand by gently blowing away
the mix, and sprinkling in the sand. Will be very careful!

Thanks for the tip.
Happy Holidays!

Merry Christmas Holidays to you too!

I recently bought a blower/vacuum to clean out my PC....it worked great, but also
made it a piece of cake to replace the top layer of perlite/succulent mix with
course sand from our local outback.


Before

After


It's very versatile, has several useful attachments, and will save
having to buy canned air. It holds a charge very well, and was able to
do the computer & plants on the same charge with no decrease in power.

"PeroBuno Air Duster, Keyboard Cleaner, Vacuum & Compressed Air & Blower 3-in-1, 35000 RPM Electric Canned Air Kit, Cordless Air Can for Computer Desk Electronics Dust Cleaning, Rechargeable Battery" $31at Amazon.

Hey, thanks for the info, Cal. You've got some nice-looking semps there!

I do not use gravel for my succulents..either pumice or insoluble crushed granite..or sometimes I also add kanuma or akadama..if I have them on hand.

Our growing environments differ..so it all depends too on ones rain frequencies, seasonal light and heat levels.

My area gets cold down to 30F overnight and we get some winter rains but no snow. So it becomes imperative to use cacti mix with added pumice and a thin layer of gritty material to protect further the base of the plant and the leaves touching the wet media.

During our long hot and dry season when temps easily soar to 100F..having gritty media and gritty top dressing allows me to water them generously and let them dry out faster, so their roots have good airflow easily. Semps are quite shallow rooted too, so it will not want to be staying too wet at the rootzone.

Johannian said:Hey, thanks for the info, Cal. You've got some nice-looking semps there!

Thanks Johannian.

BTW, what size do you mean by "gravel"?
I use natural granite I get from the desert, and grade it
to 1/16 ~1/8", and a few random sizes so it doesn't
look too perfect.

Runoff in the desert produces clean coarse granite.
I sift it in a colander before using it in potting soil
or as a topping.

I've never used gravel, only perlite for my semps. Not that I've owned many, anyway. Chicken grit is the #1 recommended gravel though, I've heard. Lynn (valleylynn) also recommended it to me when I first got into semps.