Herbs & Botanicals
Dryopteris (guan zhong)
What is dryopteris? What is it used for?
Also known as the basket fern, dryopteris is a small, leafy plant that grows in east Asia, particularly Japan, China and Korea. The rhizome, the part of the plant that grows underground, is used in herbal preparations. It is harvested in late autumn and early winter, stripped of its fibrous roots, then dried in the sun and cut into slices. The rhizome can be used either raw or after being charred.
According to the doctrines of traditional Chinese medicine, dryopteris has bitter and slightly cold properties, and is affiliated with the Liver and Spleen meridians. Its main functions are to kill parasites, to stop bleeding, and to clear heat. For centuries, an oil obtained from dryopteris has been prized for its ability to rid the body of intestinal parasites such as tapeworms. Many practitioners also use dryopteris to treat conditions such as blood in the stools and dysentery.
How much dryopteris should I take?
The amount of dryopteris to be used depends on the condition being treated. The typical dose is between 10 and 15 grams. If it is combined with other herbs, smaller amounts (4.5-9 grams) can be used. Carbonized dryopteris is used to stop bleeding, while the raw herb is used for parasites and remove toxins. However, dryopteris should be used only under supervision of a licensed health care professional familiar with the herb's properties. Patients should never self-medicate with dryopteris.
What forms of dryopteris are available?
Dried dryopteris rhizome can be found at many Asian markets and specialty stores. Powdered dryopteris and dryopteris oil are also available, and many herbal formulas contain varying amounts of dryopteris.
What can happen if I take too much dryopteris? Are there any interactions I should be aware of? What precautions should I take?
Dryopteris is considered slightly toxic, and carries with it a variety of warnings. The American Herbal Products Association has given dryopteris rhizome class 2A, 2B, 2C and 3 ratings, which mean that the herb:
- is for external use only, unless otherwise directed by an expert qualified in the use of the described substance;
- is not to be used during pregnancy;
- is not to be used while nursing; and
- should be used only under the supervision of an expert qualified in the appropriate use of dryopteris.
The German Commission E has recommended against oral administration of dryopteris due to concerns about its safety, and does not recommend external application of the herb. In addition, Canadian regulations do not allow dryopteris to be used as a non-medicinal ingredient for oral-use products. As always, make sure to consult with a licensed health care provider before taking dryopteris or any other herbal remedy or dietary supplement.
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- Landergott U, Kozlowski G, Schneller JJ, et al. The importance of recent population history for understanding genetic diversity in threatened species, with special reference to dryopteris cristata. Fern Gaz 2003;17(1):39-51.
- McGuffin M, Hobbs C, Upton R, et al. (eds.) American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, 1997, p. 43.
- Mickel J. Ferns for American Gardens. New York, Hungry Minds, Inc., 1994.