Dry soil conditions and mechanical shaking to remove excess soil is desirable before washing. Subsequent washing using a rotary root washer is necessary to remove all soil. Soil is held very tightly in the crown of the plant, and the root mass should be broken into smaller pieces to enable effective washing. Also, the separation of root and chopping the rhizome into smaller pieces is necessary to ensure uniform drying. The best method of drying to prevent enzymatic breakdown of the constituents is to dry the crop as rapidly as possible without overheating.
Overseas study provides some direction.
New Zealand studies are underway to verify these recommendations. There appear to be no general chemical tests for quality although essential oil or valepotriate content have been used as measures of quality. Individual companies use their own in-house standards to assess quality, based on experience and basic chemical tests. There is also potential to use organic production systems and there is often a premium price for such a product. The volume of valerian root traded is unknown, but traded values suggest that it is hundreds rather than thousands of tonnes annually.