Researchers in the Dept of Agriculture at the Federal University of Lavras (Brazil) devised an experiment to measure Verbena gratissima essential oil yields using various potencies of homeopathic Phosphorus. They found that Phosphorus provided the greatest amounts of "beta-pinene, trans-pinocarveol, trans-pinocamphone and trans-pinocarvyl acetate in comparison with controls," and that 9C had the greatest effect on oil yields and biomass.
Read more: http://www.ncbi.nlm.nih.gov/pubmed/22164793