I have started streps in pure vermiculite with no problems. The trick is to use very small pots and to keep the vermiculite only slightly damp. I have never had any problems with rotting or excessive moisture retention.

How small a pot? Right now, my leaf is in a 3oz cup. I guess I'm just keeping it too wet. It's so much better at staying wet than those other mixes, so I guess I'd better go light on the water.

Your conclusion sounds obvious. My hairbrained theory on using vermiculite--when it dries out it can pull moisture out of the plant. Once I had a succulent of a type very prone to rotting and then very quickly dying. I rescued a tip from a rotting plant once by putting it in vermiculite in a pot on a bright window sill. The next thing I knew, it had healed and quickly filled the pot with roots as the roots chased the remaining moisture down. The problem then was that I had a root ball full of vermiculite. The only solution then was o cut off the roots to bare nubs and start again in succulent mix.

So, I am thinking that by letting the vermiculite go dry you may get the rot process to reverse. Or, if you have roots, even if very short, why not repot into 1-1-1 and go from there. When my mom lived in Chicago she had a little covered propagation tray from Parks sitting on a counter in the kitchen. In it she had seeds, cuttings, leaves etc. of all kinds of plants, all growing in straight vermiculite. She would pull them out as they were ready to pot up. I generally don't like mixing things in community situations but it worked for her in the (sigh) 70's. Oh, and it sat on a counter that had a heat register underneath it, so had bottom heat. I bet that really helped.

Jon