Significance

• Plants grown in containers are more susceptible to cold and the alternating freeze to thaw rhythms across winter. Since the containers are not insulated by ground soil, air temperatures fluctuate and penetrate more deeply into the potting soil.
  
  

Misconceptions

• It's not only the plant species' natural ability to withstand freezing temperatures that determines survival, but also exposure to drying winds and soil moisture. Soil must not fully dry out, even with dormant plants. Roots need to remain barely moist. Dry soil shrivels the roots and weakens the entire plant.
  
  

Prevention/Solution

• If uncertain if your container plant can survive the outdoor winter temperatures, relocate it to a cool, sheltered location such as an unheated garage or shed. Ideally, this location provides temperatures between 15 and 40 degrees Fahrenheit.
  
  

Expert Insight

• Know the identity of the plants you grow in containers and their USDA zone hardiness range. To ensure best winter survivability, grow only plants rated one to two zones colder that your garden's USDA zone designation. These plants can tolerate the colder conditions in the container. For example, if you live in USDA zone 6, grow container plants that are hardy to zones 4 and 5.