The one thing the southern states had was moist ground a lot of the growing season. Not sure of Tennessee but Kentucky and around there they would only water a couple times per grow or none. I assume Tennessee was the same as my brother always talks of how humid it was there.
I wanted to grow here in socal, but unless you planted by a stream or spring( always people around them, unless you hike DEEP into the wilderness) you are watering a lot thru the season. I tried to do a grow in the spring after a good rain, but it all dried up in the area I planted some time later, and there was no way to water it without getting busted. I did that in another area, but the bugs/animals got them.
Did not know Tennessee was so productive in selling pot. I assumed most was kept local and some going out of state for higher prices. Kentucky Bluegrass, Gainesville Green, Matanuska Thunder Fuck and some others gained fame during that time.
The guys that were able to grow lots of plants here, would hike deep into the forest or other wild place, then have pump irrigation from a stream to water the plants. More work than I was up to doing. Risk as well. In a place like Kentucky, you could just plant the clone or vegging plant, even just use seeds. Plant after a rain and walk away. Come back in October and see if there are buds to harvest. They would fertilize the hole for the plant, but sometimes did not and it worked out too, depending on the soil.