Just thinking here, I bet time of year did have an effect. Think of this, I know you've heard me say the best thing to do is condition roots in the fridge for a couple weeks or so before drying them if you have the time. Well, keep in mind, that like most of the woodland plants, they tend to lose much of their moisture after they drop seeds. Bloodroot normally senesces after seeding. In the fall, ginseng is getting ready to senesce for the winter, and therefore, much of the moisture that is in the plant dries up. By putting the roots in the fridge for a few weeks, we cause them to go into full dormancy -the starches change to sugars and the moisture moves from the inside to the outside and evaporates slowly. This normally results in light, corky root which is more desirable.
It would be interesting to see a study on this.