Brackenfern, Pteridium Aquilinum (L.) Kuhn 1

Weed Technology. 1999. Volume 13:429-432 Intriguing World of Weeds iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii Brackenfern, Pteridium aquilinum (L.) Kuhn 1 LARRY W. MITICH2 In June and in August, as well doth ap ETYMOLOGY peere, Pteridium is from pteron, feather or wing, alluding to Is best to mowe Brakes of all times of the shape of the leaves. The fronds of a large plant of the Yeere. brackenfem resemble the great wingspread of the eagle, (Thomas Tosser in Five Hundred Points hence the specific name from Latin, aquila for eagle. It of Good Husbandrie, 1557) . is in the Dennstaedtiaceae (Hyam and Pankhurst 1995). Linneaus described Pteris aquilina L. in Species Plan tarum in 1753. Pteris is the Greek name for fems, from INTRODUCTION the fancied. resemblance of their leaves to the wings of birds (Britton and Brown 1896). But in 1760, Giovanni Brackenfem, Pteridium aquilinurrJ., is the only species Antonio [Johann Anton] Scopoli (1723-1788) trans of the monotypic genus Pteridiurn: one of the most fa ferred it to the genus Pteridium in Flora Carniolica. The miliar plants in the world. It encompasses several sub type is Pteridium aquilinum (L.) Kuhn (Britton and species and varieties, and its distribution is worldwide in Brown 1896). temperate,m1d tropical regions. The Although it is generally conisdered that Scopoli adopt genus Pteridium is· on all the con ed Pteridium, named by Johann Gottlib Gleditsch tinents, including Antarctica, and (1714-1786), as a segregate genus from Pteris L., thus may be one of the most widely dis making Pteridium the earliest valid generic name under tributed vascular plants on earth the International Rules, some taxonomists have argued (Cody and Crompton 1975). that Scopoli proposed it as a substitute name for Pteris Pteridium aquilinum is the most L. In order to meet this controversy, Pteridium has been familiar · northern hemisphere conserved (International Rules of Botanical Nomencla brackenfem complex, all of whose ture, 131[1935]) (Tryon 1941). members are distinctive in morphology, phenology, and Bracken or brake refers to the masses in which it general ecology. This complex forms a broad band grows. Braken first appeared in the English language in across most midlatitudes of the Northern Hemisphere 1483, as recorded in Cacholicon Angelicum, an English and spreads significantly further south in some regions, Latin Wordbook. In 1523, John Fitzerbert in his A Newe such as Africa. The distribution and ecology of the com Tracte or Treatyse Moost Profytabe for all Husbandry plex follows largely the north temperate deciduous for Men wrote, " yet [it] may be lawfully [to] selle all the ests (Smith and Taylor 1995). It is a weed of 20 or more wode, brome, gorse, fyrs, bracken, feme, busshes ... " crops in 65 countries (Holm et al. 1997). (Simpson and Weiner 1989). There are more studies covering a diversity of topics on Pteridium than on any other fem (Tryon and Tryon DESCRIPTION 1982). In addition to the stress brackenfem puts on the land and its flora and fauna, it competes directly with Pteridium aquilinum is a complex species consisting the food and forage plants of agriculture (Holm et al. of 12 geographic varieties. Subspecies aquilinum has 1997). It is the first of the plants to repopulate burned eight varieties and ssp. caudatum has four. Although woodlands or pastures. each has distinctive characters, they are difficult to define precisely because they are both phenotypically and ge netically variable (Tryon and Tryon 1982). ' No. 65 of the series "Intriguing World of Weeds." In Pteridium aquilinum the rhizome is subterranean, 2 Extension Weed Scientist Emeritus, Department of Vegetable Crops, Uni versity of California, Davis, CA 95616. extensively creeping, repeatedly branched, and invested 429 MITICH:BRACKENFERN DISTRIBUTION Fems have been evolving for about 200 million yr, and brackenfem and its near relatives for 55 million yr (Holm et al. 1997). In the Holocene, it was present as a dispersed species, spatially limited and substantially sup pressed by woodlands. About 50,000 yr ago in the late Neolithic period, brackenfem spread into new areas as wandering nomadic life declined and more permanent communities with adjacent pastures and cropland arose. More favorable lighting conditions in clearings led to enhanced photosynthetic rates and to a larger exchange of moisture and nutrients by the fem (Smith and Taylor 1986). Deforestation, necessary for buildings and fuel, per mitted greater encroachment by the fem. Land was need ed for livestock, but in medieval times the larger animals such as cattle (Bos spp.), horses (Equus caballus), large sheep ( Ovis aies), and goats ( Capra hircus) tended to Brackenfern, Pteridium aqu~linum (L.) Kuhn · keep brackenfem under control by foraging and tram pling. Now smaller sheep are more selective in foraging, with hairs but not scales. The stele, a perror_ated sole cannot tolerate brackenfem, and do not trample and nostele, and true vessels are present. Fronds are alternate, crush the fem as the larger animals had (Taylor 1988). large; stipe relatively long\-11ie vascular bundles numer Brackenfem clones in Finland have been estimated to ous. The blades are coarse, pinnately divided, usually be about 1,500 yr old, making them the oldest living tripinnate, the lower pinnae with nectaries at the base. things in the contemporary landscape (Page 1976). · · The segments are numerous, ovate to linear, the margin It is found at 3,000 m elevation in East Africa and revolute; veins free; sori marginal, mostly continuous; Japan, at 3,250 min the Rocky Mountains (U.S.), and sporangia borne between the outer indusium, the modi in the temperate climatic zones of the Andes Mountains fied margin of the segment, and the inner indusium. The in South America. The plant does not tolerate extreme receptacle is a vascular strand connecting the vein ends, heat, yet is found at sites a few degrees from the equator the inner indusium arising, at its inner side. The spores in the Galapagos Islands (where craters rise to 1,700 m) are brown, very finely spinulose, tetrahedral-globose and in Burundi in East Africa (2,800 m) (Holm et al. (Tryon 1941). 1997). The species can be a pernicious weed in tropical Brackenfem leaves are usually 1 to 2 m tall, but those America (Gliessman and Muller 1978). growing in thickets or under small trees mayu be semi scandent on the branches and reach a length of 4 or POISONOUS PRINCIPLES rarely up to 7 m (Tryon and Tryon 1982). Pteridium has several anatomical and morphological Brackenfem appears to have several chemical com features that are unusual in fems. There are true vessels pounds that cause serious illnesses in humans and stock in the stem, which rarely occur in pteridophytes. There animals but apparently is poisonous to livestock only are two types of stems: one is a long shoot that branches when eaten exclusively and in large amounts. Formerly, but does not bear leaves, the other is a short shoot that there was a high incidence of human stomach cancer of usually bears a single leaf during a growing season. obscure origin in Japan and North Wales. This may be Glandular areas or nectaries occur at the base of the pin related to the consumption of carcinogens in milk from nae and exude a substance attractive to ants (Tryon and bracken-fed cows or in freshly cooked or canned bracken Tryon 1982). shoots. The hazard is greatest to young children (Everist When ripe, the fruiting fronds have a continuous edg 1974). ing of brown sporangia, which at first are covered by The plants have been shown to be equally toxic in the reflexed margin of the leaf, but later, as the spores green forage or in a dry condition (Tryon 1941). Rhi mature, this is pushed away (Georgia 1942). zomes appear to have about five times the toxicity of 430 Volume 13. Issue 2 (April-June) 1999 WEED TECHNOLOGY fronds (Kingsbury 1964). Poisoning is difficult to detect Brackenfem deters invasions from other plants by re and diagnose, due to a delayed toxicity (Evans and Ma leasing allelopathic compounds from standing fronds in son 1965). Symptoms and death developed as much as the summer and from decaying vegetation in fall and 8 wk after animals had ceased to eat brackenfem (Kings winter. These compounds and the physical dominance of bury 1964). Poisoning is responsible for many livestock the large plant structures serve to weaken and discourage deaths, mainly of cattle and horses, but to a much lesser other competitors (Holm et al. 1997). extent of sheep and swine (Sus scrosa) (Braid 1959). In England, brackenfem is generally distributed in Brackenfem poisoning is synonymous with chronic most rough grazing areas and in many old permanent and acute enzootic haematuria in cattle ( "redwater dis,. pastures in almost every part of the country. Many of ease") and causes vitamin B1 avitaminosis in horses and the early authors dealt with the loss of grazing due to other nonruminants (Cody and Crompton 1975). this fem. Wrote Mortzmer (1708), "I have seen the Roots of it in some Grounds, eight Foot deep. The best WEEDINESS cure is often mowing of it while in grass. If you plow it up, plentiful dunging of it and Ashes are very good: but Brackenfem is "the permanent ecological opportun the certainest cure for it is Urine." ist." Its polymorphism, coupled with an exceptional tol Toe plant can survive burning and cutting because erance to a broad range of climates, environmental pa new fronds will arise from the deeply buried rhizomes. rameters, and edaphic factors, has made it the most suc In the place of an original frond bud, two expanded cessful of the fems and fem allies (Page 1986). Brack fronds and 25 frond buds developed. These buds do not enfem roots penetrate the soil ~p to 60 cm in solid all develop at the same time, but the younger ones form blocks of rhizomes from whlch lateral, ascending a reserve, which soon take the place of the first set of branches arise (de Bray 1978).

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