Why some leaves propagate and some don't? The bigger and plumper the leaf, the more successful it will propagate. Some succulents just don't do well via leaf propagation and they are Aeoneum, Kalanchoe, Sempervivum (propagate via chicks or offshoots). Most plump and hardy Echeveria leaves will be successful. Also, give them time. Some fat leaves take their sweet time to grow roots or plants. Patience is Key!
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