Answer: Plants growing in containers are far more susceptible to cold damage than they would be planted in the ground, mainly because their roots are not insulated from the cold they way they would be in the ground but also because the soil tends to dry out faster in containers. It would be less risky if you could sink them temporarily in the ground and then replant them in the boxes come spring. Alternatively maybe you could move them to a sheltered location out of the wind and mulch the containers heavily. Also be sure to keep the soil evenly moist until it freezes. You could also consider bringing them indoors as houseplants for the winter then taking them back outside next spring. You may have to experiment to see what works best for you.
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