Growing citrus in zone 8b can be done if the grower is willing to provide freeze protection (covering, old style large bulb christmas lights, etc.) during hard freezes. The trick to being successful is to plant in a sheltered location by a south wall, cover and protect whenever there is a CHANCE of a hard freeze even if the forecast is calling for a low of 28-29, too often the actual low is 8-10 degrees below the forecast temperature, and all it takes is to skip the covering one time, particularly in the first few years and you can loose the tree. Combine this with a cold hardy citrus like Satsumas for the best results, but even less cold hardy varieties can survive if you are willing to stay on top of the freeze protection, which may include having a standby generator in case of winter storm power outages.