In the spring I attended a hypertufa trough building workshop and planted two it with succulents I bought at a local garden shop. My two troughs lived happily outside on the welcoming platform. When our first hard frost was threatened I brought my troughs inside and  they are now living on a broad southern windowsill in our unheated Great Room. I wasn't worried about the hardiness of the succulents, only the troughs. I haven't paid too much attention…