Answer: Basically, you will need to check the soil moisture until the soil freezes. If the soil is dry an inch or so down, water a bit. Test it with your finger to see. You do not want to make the soil soggy, only a bit moist. To be honest, I would be equally concerned about the soil and roots freezing. If possible, move them out of the wind and try to insulate the pots. Some possible methods would be to sink them in the ground for the winter (preferred method) or try surrounding them with a thick layer of mulch or perhaps wrap them in bubble wrap or some other form of insulation. Remember too if they are in terra cotta pots, that terra cotta will probably be damaged if not destroyed by freezing weather. Good luck with your clematis!
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