In my experience, there are three mitigating factors with freezing of plant tissues. Some varieties are indeed hardier and can take a degree or two lower temperatures (desert and high mountain varieties of many plants, for example). Micro-climates within your property can be a significant difference when it comes to tolerance of lower temperatures (wind/humidity/reflected heat and light, etc). Finally, I've noted that my plants can take some fairly low 30's temps as long as there is fairly high humidity at the time. The heavy dew that will form on the plants seems to act as an insulating blanket for the plants. Reduced growth and vigor is a sometimes result however, as most plants essentially "shut off" below approximately 44 degrees. Gardening is always more of an art than a science, so your results may vary! Best regards and good luck!
