OK, yes we are talking about the same one. I'll grab that (if for no other reason than to give it a chance to make a flower so 'we' can know what it is) and the Lithops if Ma Nature pukes up some really bad cold air down here. Still having windows open most days, lows bouncing around 45-60. Could get lucky like last winter, low for season was high 20's. TY for the info!
Under the top gravel is mostly bark. Between the 'dirt' and the bottom surface of the planter is a layer of plastic nursery flat bottoms. I cut the sides off of them, leaving about 1/2 inch lip. Turned upside-down, they are hopefully maintaining an air pocket under all. There's a layer of screen under that to make sure holes don't become blocked somehow. There's about 150 drill holes in the bottom.
