California yerba santa (Eriodictyon californicum) is a chaparral shrub of western California and SW Oregon. Its leaves contain flavonoids of potential medical importance including sterubin, hesperetin, homoeriodictyol, eriodictyol and others. Seed from natural populations of California yerba santa were collected in the wild from plants relatively rich in the flavonoid sterubin and alternatively relatively rich in eriolic acid C. Seedlings from these two sources were transplanted to the field in replicated trials. Plants were harvested after three months and the plants were divided vertically into four equal parts to determine their relative dry weight yield, essential oils, and flavonoids. Total leaf dry weight yield averaged 2.8 Mg/ha and total stem dry weight averaged 1.8 Mg/ha. Leaf dry weight was least and the stem dry weight was greatest in the lower quarter of the plants. The leaves in the top quarter of the plants had consistently higher concentration of most of the flavonoids than the lower leaves. Leaves in the top quarter of the higher sterubin plant line contained 50 mg of sterubin per g of dry weight and a total of 116 mg/g of total flavonoids while the other line had negligible sterubin. Conversely, eriolic acid C was substantial in the tops grown from seed from plants with considerable eriolic acid C in nature. Considering all the leaves, those from the higher sterubin plant line yielded a total of 101 kg/ha of sterubin, 22 kg/ha of hesperetin, 60 kg/ha of homoeriodictyol, 16 kg/ha of eriodictyol and a total of 237 kg/ha of flavonoids. Plants can be selected for the horticultural production of specific flavonoids or leaves with specific herbal properties.
