Q: My son has had a water oak sapling in a large ceramic pot for ten years. He has just moved to Virginia. Since it is in a pot, is there a limit to the cold it can take?
A: In general, plant roots are more susceptible to cold temperatures than plant stems. This is because roots grow underground, where temperature extremes are moderated by the soil. Roots do not go dormant; potted plant roots are exposed to the same temperatures that only the upper part of the plan would normally see. That said, there is a wide variation in the lowest temperature a root system can tolerate. I have seen potted blueberry plants thrive after having their root system frozen solid. I don’t know how much cold weather oak roots in a pot can tolerate. At the very least, your son should put it up close to the house or wrap it thickly with sheets of insulating bubble wrap.