USDA researchers at Ames, Iowa are screening 180 accessions of St Johns wort (Hypericum) for biologically active compounds. I hope they’ll take into account phase of the moon in their evaluations:
Research on St. John’s wort (Hypericum perforatum, Hypericaceae) herb, one of the top ten herbal products in retail sales in the United States, has shown seasonal variation and differences due to cultivation location. Levels of hypericin and pseudohypericin, the compounds to which commercial products are usually standardized, were found to vary from 100 ppm to 5000 ppm from winter to summer. This remarkable quantitative difference in compounds could account for some of the differences in commercial products whose raw materials are usually from multiple sources. Additional studies with St. John’s wort found significant variation among wild and cultivated plants sourced from around the world.