I have tried a couple different ways to propagate peperomia by leaf.
Propagation box with vermiculite was a failure.
Water was a failure.
Indoors under a grow light on moist soil was a failure.
I finally found a way that works in South Florida. On soil that I let dry out between waterings and some good morning light. I put 4 Frost Peperomia leaves in this pot and 2 grew new plants!
PILEA: I'm also trying to propagate mature Pilea peperomioides leaves. I'm not seeing a new plant but the leaf is standing up in search of the sun, which is a good sign. I've got it in my propagation box on moist vermiculite. I'm hoping to see a new plant before the 'not hot' weather arrives. I'm not expecting it, though, as the information about this plant waffles on whether or not you can grow new plants just from leaves.
