Stevia is a tropical plant and needs to be moved indoors for the winter in zones 8 and below. Overwintering Stevia is an easy process. Just find a sunny Southern, Western or Eastern window and place the Stevia plant as close to the window as possible. It will thrive in the direct sunlight when the ambient temperature is above 60 or 65 degrees Ferenheit. Water weekly and your Stevia plant will reward you all winter.
For move details, enjoy this eHow article on How to Overwinter Plants From Your Garden:
http://www.ehow.com/how_4787870_overwinter-plants-garden.html
