toneo...
I have read that some ferns are capable of negative allelopathy (see details below).
en.wikipedia.org/wiki/Allelopathy
When I am planting a bed and there are ferns present I always take the time to remove them roots and all. Or just plant around them and give some space between them and the ginseng seed planted.
I have often found nice ginseng growing right in with ferns (the kind shown in the pic below) and that is one of the most common ferns around my parts. (southern Middle TN).
You might try finding out exactly what type of fern you have and then do a google search on that type and allelopathy. That would give you some details I expect.
Best of Luck !
TNhunter