Pteridium Aquilinum L

PNW 443 • March 1993 Western Brackenfern Pteridium aquilinum L. Kuhn Var. pubescens Undw. J.P. Fitzsimmons and L.C. Burrill

Brackenfern (Pteridium becoming rounded at the tips. aquilinum) is a native plant Leaf stalks are shiny yellow common throughout the with a brown, velvety base. Pacific Northwest under a variety of growing conditions. Plants spread by rhizomes and It survives in the sun or partial spores that are produced on shade, in deep, rich soils, the underside of the leaf heavy clay, or hard packed margins. Spores are brown gravelly soil. and protected by inrolled leaf margins and are produced late Preferred conditions are in hill in the growing season. Plants land and mountain canyons turn brown and die back in with deep, rich soils and low the autumn. Brackenfern is a humidity. Under these condi- member of the fern family, tions, the plants may reach Polypodiaceae, or more re- their maximum height. Brack- cently, Dennstaedtiaceae. enfern is one of the first plants to colonize logged or burned sites and is not classified as TOXICITY Figure 2.—Mature Western noxious in Idaho, Oregon, or Brackenfern affects most types brackenfern plant. Washington. of livestock. Symptoms de- velop long after the animal enzyme that breaks down The inrolled leaves or fronds first ingests the plants. Thi- thiamine, a B complex vita- of young brackenfern are aminase is present in either min) is toxic to horses and often found on lists of edible fresh or dried plants and in pigs. Feeding experiments wild plants. Now, however, the rhizomes. Thiaminase (an have established repeatedly the young plants are sus- that a large amount of bracken pected of having the potential is required to produce symp- to cause cancer when eaten. toms. Typically, a diet of hay As the plants mature, they containing more than 20 become poisonous to livestock percent brackenfern produces and humans. symptoms in about 1 month.

Cattle and sheep are resistant to IDENTIFICATION thiaminase toxicity because Brackenfern is a perennial bacteria in the rumen usually plant, growing from hairy, produce sufficient amounts of creeping rhizomes. Leaves (fronds) are broadly triangular in outline, reaching 6 feet in Jim P. Fitzsimmons, graduate student, crop and soil sciences; and height. The leaves are doubly Figure 1.—This young frond has Larry C. Burrill, Extension weed compound at the bottom, just started to unroll. specialist, Oregon State University.

A Pacific Northwest Extension Publication • Oregon • Idaho • Washington thiamine. Brackenfern poison- grass is recommended. Pile ing in cattle from unknown and burn the rootstock re- USE PESTICIDES SAFELY! toxins can follow ingestion of moved by harrowing to large amounts of green or dried eliminate sprouting. • Wear protective clothing fronds over an extended period. Mowing reduces spore pro- and safety devices as The symptoms are sudden, duction, helping prevent their recommended on the label. brief, and usually fatal. Sheep spread, and allows more light Bathe or shower after each poisoning with bracken has not to reach the grass. Brackenfern use. been reported. is less aggressive in estab- • Read the pesticide label— lished vegetation. Manage even if you’ve used the If ample forage is available, pastures infested with pesticide before. Follow livestock usually avoid eating brackenfern for maximum closely the instructions on brackenfern. Animals accus- growth and survival of desir- the label (and any other tomed to grazing among these able forage species to compete directions you have). • Be cautious when you plants usually avoid them or with brackenfern. apply pesticides. Know may develop an immunity to your legal responsibility as the toxin. If livestock are Herbicide registrations change a pesticide applicator. You introduced into an area with frequently; therefore, this may be liable for injury or brackenfern, high amounts publication does not contain damage resulting from may be eaten, especially if specific herbicide use instruc- pesticide use. other forage is not available. tions. Registered uses are summarized each year in the Pacific Northwest Weed Control CONTROL Handbook. Clean cultivation prevents establishment or eventually In addition, detailed instruc- kills the rootstock. tions for herbicide use are provided on herbicide con- Brackenfern rarely is a prob- tainer labels and in other lem in fields receiving peri- literature provided by herbi- odic cultivation. In recently cide manufacturers. cleared or burned areas, deep plowing, followed by harrow- ing, and seeding to a perennial

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the Oregon State University Extension Service, O.E. Smith, director; Washington State University Cooperative Extension, Larry G. James, interim director; the University of Idaho Cooperative Extension System, LeRoy D. Luft, director; and the U.S. Depart- ment of Agriculture cooperating.

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