Charleston straddles USDA Plant Hardiness Zone Ho-Hum (or 8b), with minimum temperatures of 15-20 degrees, and USDA Plant Hardiness Zone Ooh-La-La (or 9a), with minimum temperatures of 20-25 degrees. What grows in Zone Ooh-La-La? Think tropical hibiscus, some bromeliads, an expanded range of palms, tropical ferns. I want that! So I keep shoving more marginal plants under the protective canopy of my live oak.
A live oak can help gain those few precious degrees that mean a tropical that would normally die is instead root-hardy (hopefully the case with the monstera) or that a tropical that normally would only be root-hardy is evergreen (for example, the Persian Shield). On a cold night, the closed canopy of the live oak acts like a cozy down blanket by trapping the warmer air radiated up from the ground. That same "blanket" also prevents plant cell damaging frost from settling on leaves and stems.
How much of a difference does it make? Seeing is believing. In a downtown Charleston park, this Persian Shield, lying just a few feet outside the dripline of a Live Oak, was top-killed by freezing temps a few days ago:
Same story with this groundcover which is also outside the dripline of the Live Oak:
If these plants all thrive this winter, my azaleas and holly ferns had better watch out... Zone Ooh-La-La will be moving on in!