Mrs D - Gardengirl is from the Carolina's (from what the line under her avatar says).

So I guess they don't get the freeze we get up here. But my brother - who lives near me, not far south of lake Erie, has a couple plants buried in container. In those beds, they keep them from heaving by covering with rock for mulch.

I think as long as the dirt and cover are heavy enough, you can get away with it. The planter has holes too, and if the plant's roots get though and grab outside dirt, that'll help.

You are so right about the Water Grabber stuff. All potted plants should have that. Hyponex's soil has that plus slow release food built in. I used that in my nail keg palnters - it was worth the extra couple bucks.

I can't believe all the stuff that's coming up already. Something else every time I look. Today, I see iris turning green, mullien, campanula, columbine, false sunflowers and fresh growth on the lavender.