I am from the southern middle Tennessee area and have been hunting seng since around 1976..
I have always noticed MaidenHair Fern (MHF) and Bainberry as being very good seng companion plants. There is also another spindly vine type plant with clusters of 3 leaves which is called American Hog peanut. When we find the hog peanut growing nice and thick and healthy looking - there is usually seng nearby.
In my opinion the MHF is the absolute best companion plant for seng.
In Scott Persons book he gives this list of "plants that are known to grow right along side of ginseng".
MHF, rattlesnake fern, christmas fern, baneberry, yellow lady's slipper, blood root, blue cohosh, black cohosh, wild ginger, solomons seal & false solomons seal, jack-in-the-pulpit, trilliums, form flower, jewelweed, mayapple, goldenseal, sweet cicely, yelloy mandarin, dutchmans pipe, bedstraw, liverwort, canadian violet...
But he goes on to say...
Some of these companion plants are cal-cicoles (normally growing in calcerous soils) and need conditions nearly identical to ginseng. Then he gives this short list of those..
1.. MHF (MaidenHair Fern). He list this one first.
2.. Yellow Lady's Slipper
4.. Blue Cohosh
I think he listed MHF first - because he agrees with me
Below is a youtube vid of mine showing some MFH, hog peanut and a 4 prong seng plant.http://www.youtube.com/watch?v=NiZiUFxuPc0&list=UUef1LCgEcWnpIq3tFX4J-VA&index=1&feature=plcp
Below is a nice pic of some MHF and look just up the hill from it.. a couple of nice old seng plants.