About Cold Hardiness
Every plant species is adapted to the growing conditions in the region where it is native or has been growing successfully for years, and each grows best elsewhere only wherever climate and temperatures are similar to these familiar conditions. Because they can withstand the coldest winter temperatures in these areas, they are described as “hardy” there. For instance, a camellia may be cold hardy in Georgia where it lives normally, but it not in New York where winters are more severe.
The cold hardiness of each plant is a concern because the typical residential yard is full of plants that are from other regions with varying maximum winter temperatures. While they are probably basically winter hardy for your yard (because they have survived several winters there already) individual ones may be only marginally so, experiencing stress during the cold that reduces their vigor and pest resistance year round. Others, while hardy, may be inherently brittle or shallow rooted and easily damaged by winter weather. In either case, these plants would benefit from some winter protection.

Tip To Protect Transplants

Add Frost Protection To Transplants
One trick for protecting new transplants in danger of being hurt by frost is to apply a foliar spray of diluted seaweed extract (one teaspoon to the gallon of water) just before nightfall when frost is expected. Seaweed administered just before frost helps stop cold damage by increasing the sugar content in plant cells, thereby lowering the freezing point of the sap. For more information go to Using Seaweed In The Landscape in Yardener’s Helper and Seaweed and Kelp Products in Yardener’s Tool Shed.