Hmm, every semp I've ever seen for sale in a pot seems to have an organic soil mixture with some perlite tossed in. I guess that's a cheap and easy propagation medium.
Here's my first attempt at a gravel surface covering. I gotta say water zips right through it. I'm hoping it will minimize dirt splashing in a hard rain.
It does have a tidy appearance. It will only look better and better as the semps mature.
I'm guessing the semp chicks have a way of getting new roots down through gravel like this.
