Arky...
Where I live her in Middle TN... we don't have mountains... just hills and hollers.
In my County the highest elevation is around 1100... and low is in the 600 range.
It is very common for me to start looking down a hollow (from the head down) and up closer to the head of the hollow... when a creek does start there will be gravel bottom to creek... but then as you go on down the hollow, that will eventually turn to hard slick rock bottom.
Where it turns to slick rock bottom, you may go on down the hollow a little ways and there will be a drop in elevation and a water fall and then you start seeing rock above ground (rock outcroppings) and stuff like that.
That is when I usually start finding ginseng in a hollow real good, when you get to that point.
That usually happens below 750' elevation.
It is somewhat rare to find seng above 800' here in my county, but that does happen, mostly on hillsides that face due north, or up near the head of a side hollow on a hillside that faces near due north.
Now keep in mind we don't have mountains here and that probably changes the game a lot. I know Billy and others find seng at very high elevations in the mountains...
For me.. if a hollow does not go below 750-800' it is pretty much a waste of time looking.
Most of our larger creeks in the county are down in the 600-680' level and the creek bluffs along side them are places that I find some really good seng in. On those creek and river bluffs... usually around the bottom quarter to half of the bluff, where you have flats up on the bluff you can find some really good seng.
The roots below all came off of a creek bluff, at around 650' elevation.
Good Luck
TNhunter