Feverfew
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Description
Feverfew (Tanacetum parthenium (L.) Schultz Bip., Asteraceae) is a perennial herb with erect stems growing to one metre tall. The leaves are alternate, divided into broad, toothed segments, and have a strong distinctive odour. The flowers are daisy-like, having a central disc of yellow florets surrounded by white ray florets, and form flat-topped inflorescences (flowers). For cultivation of medicinal feverfew it is important to understand that there are at least three types of feverfew that have significant differences in their natural chemistry. These types cannot be distinguished visually, only by chemical testing.
History And Use
Feverfew has been used in Europe for centuries to reduce fevers and swelling, in the treatment of arthritis, asthma, female reproductive problems, toothaches and headaches. It has been used to relieve indigestion, as an air purifier, and as an insect repellent and balm.
Feverfew leaf’s main modern use is in the prevention of migraine headaches. It is not a painkiller and cannot be used to treat a headache in progress, but when taken continuously it can gradually (over a period of months) reduce both the number and severity of the migraines, with few side effects. There is clinical proof of feverfew’s effectiveness when the correct variety of feverfew is administered as dried leaf material in tablet or capsule form. An alcoholic extract was shown to be ineffective. Other uses include treatment of menstrual pain, asthma, rheumatism and arthritis. However, a clinical trial of feverfew as a treatment for rheumatoid arthritis found no significant benefit.
Economics And Marketing
Feverfew is one of the top 20 herbal supplements in terms of sales in natural food stores, comprising 1.6% of sales in 1997. In Europe, feverfew outsells aspirin as an anti-migraine treatment. There are currently 11 feverfew products registered with Health Canada, 10 as tablets, caplets, or capsules made from the leaves for the prevention of migraines, and one other product formulated as drops, globules, and granules for homeopathic applications.
Feverfew is also in demand in the dried floral industry, as the flowers retain their colour and do not shatter when dry. There may be potential as an insect repellent.
Area Of Adaptation
Feverfew is believed to have originated in temperate Eurasia, but it is now cultivated as an ornamental and medicinal herb and naturalized as an escapee all over the temperate world. Widely adapted to many situations, it does especially well in dry conditions, and tolerates poor soil.
It is found in waste places and along roadsides.
Site Selection
Feverfew does best in average quality, well drained soil of pH 6.0 - 6.7 (6.3 optimum). It prefers full sun or partial shade. It is listed as being suited to hardiness zone five but has been overwintered successfully in zone four without protection and provision of a mulch cover should allow it to overwinter in zone three.
Planting/Transplanting
The type of feverfew proven effective in the clinical trials is rich in parthenolide, (active ingredient) the level of which varies widely in feverfew from different genetic lines. Thus seed should be purchased only from a supplier who can provide evidence that the seed comes from a parthenolide-rich type of feverfew. Feverfew seeds require light for germination and should be sown on the surface of the soil and lightly tamped in. Seeds should be sown approximately two weeks before the date of the predicted last frost. Germination occurs in 10 - 15 days. Keep the seedlings at a daytime temperature of 65 to 70 degrees F (18° to 20° C) and 50° F (10° C) at night. Seedlings should be transplanted in small clumps of about five seedlings when 0.5 to 0.75 inches (1 - 2 cm) tall, e.g. in June, spaced 9 to 12 inches (25 - 30 cm) apart. Water every second day until established. Flowers should be pinched off to encourage vigorous leaf growth and bushy plants in the first year. Experiments at the Crop Diversification Centre in Edmonton showed that feverfew is easily grown in the greenhouse by germinating in a soilless medium at 22° C and transplanting to eight inches (20 cm) apart. A complete nutrient fertilizer was used on the seedlings. The first crop was harvested after 10 weeks, with a second cut 27 days later. Thrips and aphids were two potential problems in the greenhouse trials. Plants which were allowed to become rootbound were found to have the highest levels of parthenolide.
In the second and subsequent years feverfew can be divided in the early spring by sectioning each old plant into three parts and transplanting these. Cuttings may be taken by digging part of the heel of the old plant along with the new shoots that form at its base in the spring. The foliage can be shortened by three inches (8 cm) and the cutting planted in light soil in a shady spot, covered with sand and drenched with water.
Weed Control
Mechanical and/or hand weeding is required.
Insects And Diseases
There are no reports of insect or disease problems in feverfew in Manitoba.
Irrigation
Feverfew is drought tolerant and should not require irrigation unless severe conditions arise.
Harvesting
Feverfew should be harvested in the second year by swathing the leaves and flowers while in full bloom (mid July). Leave four inches (10 cm) for regrowth to allow a second cut later in the season.
Processing
Feverfew should be dried on screens out of direct sunlight for 10 - 14 days. Feverfew leaf, the only part used in registered anti-migraine preparations, is used in powdered form, best produced by a shear mill. For homeopathic purposes, a tincture can be prepared. The leaf material should be stored in a cool, dark area as it has been found that dried feverfew leaf loses at least 20% of its parthenolide content in the first year and more than 50% after two years of storage unprotected from heat and light.
Quality Control
The key to successful marketing of feverfew (and any other medicinal herb) is quality control. There are probably numerous active ingredients in feverfew working by more than one mechanism. The clinical significance of experiments done on a number of feverfew constituents is still unknown. Parthenolide, one of the substances giving feverfew leaf its very bitter taste, is probably not the main active ingredient but it is present in significant amounts (0.2 to more than 1% of the dry weight) in medicinal feverfew. Parthenolide is therefore a marker of the quality of feverfew but not a guarantee of its efficacy. Measuring the amount of parthenolide present in the crop at the time of flowering is an important step to prove that it is the correct type of feverfew. This testing can be done by any of a number of independent laboratories, the closest to Manitoba producers being the Food Development Centre in Portage la Prairie.
Having a pressed and dried specimen of the whole plant from the field is also important for quality control because there are more than 30 different plants that contain parthenolide, so buyers are on the look-out for substitution or adulteration of this valuable crop with other plants. Further quality control measures are described in Health Canada’s Good Manufacturing Practices Guidance Document at http://www.hc-sc.gc.ca/dhp-mps/consultation/natur/gmp-bpf-eng.php .
Further Information
Saskatchewan Irrigation Development Centre, Outlook, SK is currently developing basic production practices for feverfew.
Studies include:
- Direct seeding vs. transplanting stand establishment
- Seeding rate and row spacing
- Seeding and harvest timing
- Fertilizer, water and weed management
- Over-wintering and winterkill
References
Awang, D.V.C. 1993.
Feverfew fever. HerbalGram 29: 34-36, 66.
Awang, D.V.C. 1998.
Feverfew effective in migraine prevention. HerbalGram 42: 11.
Barl, B., Loewen, D., and Svendsen, E. 1996.
Saskatchewan Herb Database. Department of Horticulture Science, University of Saskatchewan, Saskatoon, SK.
Foster, S. 1993.
Herbal Renaissance. Peregrine Smith Books, Layton, Utah.
Kowalchik, C., and Hylton, W.H.
1987. Rodale’s Illustrated Encyclopedia of Herbs. Rodale Press, Emmaus, PA.
Marles, R.J., Kaminski, J., Arnason, J.T., Pazos-Sanou, L., Heptinstall, S., Fischer, N.H., Crompton, C.W., Kindack, D.G., and Awang, D.V.C. 1992.
A bioassay for inhibition of serotonin release from bovine platelets. Journal of Natural Products 55 (8): 1044-1056.
Olin, B.R., Dombek, C., Hulbert, M.K., and Golshahr, V., eds. 1994.
Feverfew. The Lawrence Review of Natural Products. Facts and Comparisons, St. Louis, MO.
Younus, M. and Mirza, M. 1997.
Research Report on the Production of Medicinal Herbs in Greenhouses During 1997.
Proceedings of the Prairie Medicinal and Aromatic Plant Conference ‘97, Brandon, MB. p. 35