Yarrow

Background

Yarrow (Achillea millefolium L.) is a perennial member of the Composite family and is native to Europe and western Asia, but has become naturalized in North America. The plant has flattened heads of white flowers and deeply divided leaves. It is adapted to a wide range of climate and soil types, and is easy to grow. Yarrow is used medicinally and in dried flower arrangements and herbal tea blends. An essential oil can be steam distilled from the inflorescence and is used by the cosmetics industry in herbal shampoos and creams. This oil is blue because of the presence of azulene, which forms during steam distillation (1).

Yarrow grows best in full sun. Yarrow may be established by direct seeding in the field or from transplants or root division. Direct-sown crops may be seeded in the fall. The plants will self-sow and spreads by rhizomes. Older plantings will decline in vigor, but may be rejuvenated by cultivating strips through the crop.

The yarrow plant is harvested during bloom, when 80% of the flowers are open. Full yield can be expected the second year of flowering. For use in herbal teas, the stems are removed by rubbing the dry material through a 2.5-mesh (8 mm opening) screen. Yarrow should be dried below 35°C (95°F) out of direct sunlight. Average yields are 1.0 - 4.0 t/ha dry herb (0.45 - 1.8 tons/acre) (2). The essential oil of yarrow is found predominantly in the flowers. According to Hornok (2), the inflorescence contains 0.2 - 0.5% oil, and the leaves and stems 0.02 to 0.07%.

Research Summary

1998

Yarrow ‘Proa’ (Johnny's Selected Seeds, 1 Foss Hill Road, RR1 Box 2580, Albion, ME 04910-9731) was sown in the greenhouse on April 4, 1998, and transplanted to the field at the Western Agricultural Research Center, Corvallis, MT on May 13. Six-row plots were 8 ft long with rows 18" apart and 12" between plants, with four replications. The top 2/3 of the plant was harvested when in full flower on August 18, 1998, and on August 3, 1999. In 1998, plants were air dried and the entire top distilled. In 1999, plants were either distilled fresh or air-dried before distillation. Distillation was not replicated because of the small amount of plant material, so the difference between dry and fresh distillation in 1999 may not be significant. Tea-grade dry matter was obtained in 1999 after screening through 1⁄4-inch hardware cloth.

2000

Yarrow ‘Proa’ and ‘Great Northern’ (accession 9057902 from the Bridger Plant Materials Center) were transplanted to the field on May 22, 2000. Five-row plots were 10 ft long with rows 18" apart and 12" between plants, with four replications. No harvest was done in 2000. The top one-third of the plants were harvested on September 20 (Proa) and August 2, 2001 (Great Northern), air-dried, and distilled.

^a Dry weight of top 2/3 of plant

^b Percent oil calculated on a dry weight basis for both treatments

^a Dry weight on top 1/3 of plant

Discussion

Yarrow is well suited to the climate and soils of the WARC and probably to most of the western US where the species is native or established as a weed. Yields of yarrow exceeded those reported by Hornok (2). The commercial cultivar ‘Proa’ and ‘Great Northern,’ a native selection from the Bridger Plant Materials Center, were similar in oil and tea grade dry matter production.

Bridger Plant Materials Center, USDA, Natural Resources Conservation Service, Rte 2, Box 1189, Bridger, MT 59014-9718

References

1. Guenther, E. 1948. The Essential Oils. Robert E. Krieger Pub. Co., Inc.
2. Hornok, L. Cultivation and Processing of Medicinal Plants. John Wiley and Sons, New York.
3. Rohloff, J., E. Skagen, A. Steen, and T. Iversen. 2000. Production of yarrow (Achillea millefolium L.) in Norway: essential oil content and quality. J. Agric. Food Chem 48: 6205-6209.
4. Simon, J.E., A.F. Chadwick and L.E. Craker. 1984. Herbs: An Indexed Bibliography. 1971-1980. The Scientific Literature on Selected Herbs, and Aromatic and Medicinal Plants of the Temperate Zone. Archon Books, 770 pp., Hamden, CT.