codielane said:I've noticed on this thread that several (most) of you have your succulents in what looks like gravel. What kind of rocks are y'all using, and should I be doing this?
I usually use chunky pumice (pieces about 1/4 inch wide) in a layer about 1 rock thick. My top dressing is not terribly different from the soil itself (which is 50% pumice sized <1/4 inch).
The top dressing provides armor against the rain, keeping the soil in its place. It also provides some armor against the sun and makes the top layer of soil available to the plant, theoretically. My plants are almost all out in the elements and I think the top dressing helps protect them from the sun and the rain. Plus it's an opportunity to dress them up and make them look nice (soil does not look nice in my opinion). For some rosette succulents a layer of top dressing will keep the dying lower leaves from coming in contact with soil, and that can help avoid rot.
The key is not to use too much or too heavy a layer of rocks on top, or you will end up entombing your plants with moisture. I believe pumice and lava rock (airy volcanic rocks) are better because they breathe, ie. allow the soil below to dry out efficiently. Some proof of this effect can be seen in the following photo where the chunky pumice I used as top dressing has changed from white to brown because of the (dirty) water that has traveled upward from the soil through the pumice and evaporated, leaving the dirt behind.
Compare the pumice around the agave to the pumice in the pots next to it (which is already starting to turn brown) and you can see how this works over time. With heavy drinking plants (that dehydrate the soil faster than evaporation) the effect is greatly reduced. The agave in the picture is definitely not a heavy drinker, it's safe to conclude.
