Data Views Total Plants: 1 CSV Excel PDF Click on column headings to sort table by that column Plant Part Low PPM High PPM StdDev *Reference Thymus vulgaris Leaf -- 3.0 Duke, J. A. Writeups or information summaries on approximately 2,000 economic plants, USDA, ARS, Beltsville, MD 20705. *Unless otherwise noted all references are to Duke, James A. 1992. Handbook of phytochemical constituents of GRAS herbs and other economic plants. Boca Raton, FL. CRC Press.