This trimmed back over-wintered geranium plant hung upside down, bare-rooted in a cool dark storage room immediately started to sprout when it was trimmed and place in a moist mix of half peat and half Perlite.) I followed the directions from this video: http://www.gardengatemagazine.com/overwinter-geraniums/

The mineral deposits referred two were around the inside top of the pot. I've never been able to get them off and they're a real eyesore.