Pteridium aquilinum

western brackenfern


The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Division - Pteridophyta (ferns)
Class - Filicopsida. Order - Polypodiales. Family - Dennstaedtiaceae (bracken fern) Genus - Pteridium Gleditsch ex Scop. (brackenfern). Species Pteridium aquilinum (L.) Kuhn (western brackenfern).

Ecology: The leaves or fronds of western bracken fern are normally from 3-30 dm long including a stipe (leaf-stalk) that may be as long as 10-15 dm but is usually shorter than the leaf blade. The blades of the fronds are divided into pinnae, the bottom pair of which are sometimes large enough to give the impression of a three-part leaf. Rhizomes are the main carbohydrate storage organs. Rhizomes also store water and are consistently around 87 percent water. Rhizomes can be up to 2.5 cm in diameter and branching is alternate.

Western bracken fern is basically a shade-intolerant pioneer and seral species that is sufficiently shade tolerant to survive in light-spots in old-growth forests. The light, windborne spores of western bracken fern allow it to colonize newly vacant areas. Western bracken fern has been documented as a pioneer on sterile, cooled lava slopes. Western bracken fern increases soil fertility by bringing larger amounts of phosphate, nitrogen, and potassium into circulation through litter leaching and stem flow; its rhizomes also mobilize mineral phosphate.

Western bracken fern is most commonly used today as a food for humans. The newly emerging croziers or fiddleheads are picked in spring and may be consumed fresh or preserved by salting, pickling, or sun drying. Both fronds and rhizomes have been used in brewing beer, and rhizome starch has been used as a substitute for arrowroot. Bread can be made out of dried and powered rhizomes alone or with other flour. American Indians cooked the rhizomes, then peeled and ate them or pounded the starchy fiber into flour. In Japan starch from the rhizomes is used to make confections. Bracken fern is grown commercially for use as a food and herbal remedy in Canada, the United States, Siberia, China, Japan, and Brazil and is often listed as an edible wild plant. Powdered rhizome has been considered particularly effective against parasitic worms. American Indians ate raw rhizomes as a remedy for bronchitis.


A very aggressive fern of worldwide distribution for dry woodlands. The only fern for most dry shade situations. Ideal for dry Post Oak forests and pine forests. The tripartite, furry, silvery fiddleheads emerge in early spring. The roots colonize aggressively and extend deep in search of moisture, as far as 10 feet deep in some locations.


The fronds are killed by frost. In northern climates they are killed each winter and new fronds grow in spring; in mild areas individual fronds persist for 2 to 3 years before being replaced. Dead fronds form a mat of highly flammable litter that insulates the below-ground rhizomes from frost when there is no snow cover. This litter also delays the rise in soil temperature and emergence of frost-sensitive fronds in the spring.

Fossil evidence suggests that western bracken fern has had at least 55 million years to evolve and perfect antidisease and antiherbivore chemicals. It produces bitter tasting sesquiterpenes and tannins, phytosterols that are closely related to the insect molting-hormone, and cyanogenic glycosides that yield hydrogen cyanide (HCN) when crushed. It generates simple phenolic acids that reduce grazing, may act as fungicides, and are implicated in western bracken fern's allelopathic activity. Severe disease outbreaks are very rare in western bracken fern.

Fire effects: Western bracken fern is considered a fire-adapted species throughout the world. It is not only well adapted to fire, it promotes fire by producing a highly flammable layer of dried fronds every fall...The fronds of plants are generally killed by fire, but some rhizomes survive. Fire benefits western bracken fern by removing its competition while it sprouts profusely from surviving rhizomes. New sprouts are more vigorous following fire, and western bracken fern becomes more fertile, producing far more spores than it does in the shade.


A single, fertile frond can produce 300,000,000 spores annually. Spore production varies from year to year depending on plant age, frond development, weather, and light exposure. Production decreases with increasing shade. The wind-borne spores are extremely small. Dry spores are very resistant to extreme physical conditions, although the germination of western bracken fern spores declines from 95 to 96 percent to around 30 to 35 percent after 3 years storage. The spores germinate without any dormancy requirement. Under favorable conditions, young plants could be found 6 to 7 weeks after the spores are shed. Under normal conditions the spores may not germinate until the spring after they are shed.

When spores germinate, they produce bisexual, gamete-bearing plants about 0.6 cm in diameter and one cell thick. These tiny plants (gametophytes or prothalli) have no vascular system and require very moist conditions to survive. The young spore-bearing plant (sometimes called a sporling) which develops from the fertilized egg is initially dependent on the gametophyte until it develops its first leaf and roots.

Most regeneration in western bracken fern is vegetative. Western bracken fern's aggressive rhizome system gives it the ability to reproduce vegetatively and reduces the plant's dependence on water for reproduction. The rhizomatous clones can be hundreds of years old, and some clones alive today may be over 1,000 years old. Rhizomes have a high proportion of dormant buds. When disturbed or broken off, all portions of the rhizome may sprout, and plants growing from small rhizome fragments revert temporarily to a juvenile morphology.

Species Distribution


USDA Plant Database
USDA, NRCS. 2016. The PLANTS Database (, 4 February 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA.

Flora of North America
Flora of North America Editorial Committee, eds.  1993+.  Flora of North America North of Mexico.  19+ vols.  New York and Oxford.

Intermountain Herbarium
Consortium of Intermountain Herbaria. 2016. http// Accessed on February 04.

Burke Museum Plant Image Collection
The plant image collection at the Burke Museum, University of Washington.

Jepson Manual
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA. $131.95, hardcover; 1600 pages. ISBN-13: 978-0520253124.