Stephen, when it comes to planting ginseng seed, it is always recommeded doing it after the rain or when the soil contains enough moist. In general, ginseng hates wetness, yet loves moisture. On the one hand it does poorly in heavy, soggy soils especially bottom lands. The roots will rot if planted in low-lying areas. On the other hand, ginseng requires at least 20 inches of annual rainfall. Lack of available soil moisture greatly reduces germination, root growth, and seed production.
FYI, the best soils are humus rich sandy roams located on north or south facing slopes with sufficient moisture even during dry spells. Hope this helps and good luck with your ginseng!