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I also purchased a USB coffee mug heater to place underneath the ceramic pot of the Mimosa - to encourage soil warmth and root growth. Dunno if this is dangerous - it doesn't get too hot yet - just hooked it up today.

Response: I have two of these I use often to start cuttings and seeds - works great for a small dab of either!

The first plant just had its sensitive leaves shrivel up and its main starter leaves get so thin that it died.

I have two more sprouting now. How do I avoid this from happening to them? Do I give it more light? Maybe more air? Less water? I used soil bought from the store.

I have some under T5 lights that are doing very good. The lights are for vegetative growth at 5000 lumen. I have them 18 hours on and 6 off. The leaves close in the dark and open a few minutes after the light comes on. I do notice after 10 hours or so that the leaves fold up even though the light is still on. I'm guessing they are getting too much. I have them along side my hydroponics and not going to adjust the time just for them. I use topsoil I bought at Home Depot, nothing special. They are not very picky and easy to grow. They go to seed after 3 months or so. The ones I have now are from last Summer's seeds.

I had some outside in a planter last summer. I notice in the direct sun that the leaves fold up and on a cloudy day they all open. Below is a photo of them on a cloudy day.