How do I overwinter hostas in pots?
Allow the plants to go dormant naturally. Maintain the moisture in the pots as you would if they were growing, or somewhere in that range of moisture but well drained. As the foilage drys up and can be easily removed (without tearing it from the crown) remove it, or snip it off with disinfected scissors. Allow the pots to freeze. If the temperature fluctuates greatly before total freeze up, move them to a location in which the temperature varies the least. After freeze up, I move mine to a varment proof room in an outbuilding (barn for me) and cover with 4-6 inches of wood shavings (the kind used for livestock bedding at fairs, etc.), and ignor till spring. If you do not have a varment proof area, it probably wouldn't hurt to add some mouse bait, although damage would be minimal since the pots are frozen. In the spring, I bring them into my heated shop about 2 weeks prior to our last expected frost date and let them thaw. If frozen properly, and with the condensation that occurs as they thaw, there is sufficient moisture to sustain the plant, but keep a watch depending on the water carrying capacity of your potting mix. I believe it is better to lean towards the dry side before watering as keeping the pots too wet invites other problems. As the new eyes appear and start to unfurl, move them outside to fend for themselves. If weather conditions (a frost or freeze) becomes imminent, move them back inside. It will not kill the plant but may make those new leaves unsightly. If you have sufficient lighting, you may leave them in longer, but I move mine out for a couple of different reasons. My lighting is not proper, and if raised in an enviornment of constant ambient temperatures, leaves & stems have no reason to develop the strenghth needed for outside conditions and besides being frail, are more subject to desiccation from wind--it eliminates the need for a "hardening off" maintenance period. If I were readying pots for the following year's use, I would make my divisions early and place the pots where they can utilize the sun to help develop good root systems and pay a lesser amount of attention to the foilage. They will reward you greatly the following year with better foilage and a root system to support it.
contributed by seedseller1