Hi Jim, you do have a challenging climate for gardening but my best advice is to keep your overwintering plants very dry until spring. Dry soil will help to keep them dormant and dormant plants can handle the weather extremes better than those still trying to produce. Even if the soil feels dry to not water. Look at the plant and if it starts to look wilted offer just a small amount of water to keep the plant from shriveling. Once spring arrives you can increase the water especially when you see signs of new growth. If your garage has windows you may want to cover them to keep out light. A cool dark spot and dry soil are your best bets for keeping plants dormant all winter. Keep growing, Marianne Binetti