Pteridium

Bracken ferns

Pteridium (from the Greek pteridion, small wing or, more often, small fern—which makes me seriously wonder about the plant author's powers of observation) is the universally recognized bracken fern. In various manifestations, all of them extremely weedy, it is worldwide in distribution, and has the honor of being the most widespread of vascular plants. Mickel (pers. comm.) jokes that they are all growing from a single creeping rhizome.

And creep the rhizome does, buried anywhere from several inches to 18 in. (45 cm) or more under ground. The deciduous fronds are usually between 3 and 6 ft. (90 and 180 cm) tall, but can be even taller. Slightly grooved stipes are the color of pea soup and up to one-half of the frond length. Blades are broadly triangular and usually tripinnate-pinnatifid with 10 to 12 pairs of very widely spaced pinnae. Sori are marginal and covered by a false indusium. Spore production, however, has decreased measurably in recent decades so many populations are sterile. Presumably they do not need to waste time reproducing from spores.

Chemically the fronds are infused with dangerous toxins. The fiddleheads, which are popular in Asian diets, are carcinogenic and responsible for much of the stomach cancer in those areas. Grazing animals are also vulnerable as the fronds are known to poison cattle, sheep, and pigs, making the bracken invasion in ranching areas, such as the hills of England and Scotland, a serious economic threat, and consequently the subject of much research. Bugs too pay a lethal price for nibbling on bracken foliage since the fronds release

Polystichum xkiyozumianum in the Kohout garden. in a contain« phnting and extend above the leafage °f companion ferns.

Polystichum xkiyozumianum in the Kohout garden. in a contain« phnting and extend above the leafage °f companion ferns.

cyanide when damaged. Pteridium asserts its dominance in the plant world as well. The toxins from decaying fronds repel competition from other plants by preventing the germination of seedlings. It even kills its own young. Technically this self-serving plant mechanism is known as allelopathy.

For informational balance, given its abundance (the original renewable resource?), bracken has a long and storied history of practical usages dating back to pre-Roman times. The applications were so critical that there were strict regulations regarding the timing of the frond harvest. A violation resulted in a fine and the loss of "cutting privileges." In Great Britain fronds were a portion of the required annual rent from peasants to their landlords. (Oh how wondrous it would be to take care of my tax burden by delivering a few truckloads of bracken fronds to the IRS.) In rural areas fronds were used as thatch. The insect-repellent chemical components rendered the cut foliage practical as bedding for stock and domestic animals (and in parts of the world is still used for help in controlling fleas) and, in desperation, as minimal mattresses for humans as well. It was used on the floors in the forts of Hadrian's Wall, for example.

Mold and insect damage control qualities made bracken an effective packaging preservative and their fronds were commonly used to wrap fruits, fish, and other perishables en route to market. High foliar concentrations of potash were returned to the soil as a top dressing for potato crops as well as an extremely important component in the production of glass, soap, and bleach, an "industry" that dates back to the 10 th century.

This eclectic assortment of multiple uses doubtless kept the outward march of bracken colonies under control. Would that the ancient value of Pteridium could be put to an applied use today. Gardeners, farmers, and certainly the overseers of diminishing crop and grazing lands worldwide would joyously welcome an economic demand for their fern crop. (The one contemporary use, which I remember from my Camp Fire Girl days, is to apply the "juice" of bracken stipes to reduce the irritation from nettle stings. It works.)

As all of the above implies, uncontrolled bracken is not an ornamental addition to gardens. It does, however, often show up as an uninvited guest. Short of using a steam shovel, removing it by digging is not generally successful. Chemical sprays or diligent removal of emerging fronds eventually destroys the invasion.

Pteridium aquilinum (like an eagle, referring to the implied wing shape of the frond) is the familiar menace that establishes territorial rights throughout the world. Rhizomes circle about, producing tall fronds on long stipes with blades that are tripinnate-pinnatifid. (True to tradition, there are even crested cultivars in Britain.) The species has been subdivided into a number of varieties basically defined by the angle

Pteridium aquilinum var. latiusculum in Georgia.

Pteridium aquilinum var. pubescens in its typically weedy manifestation along the trail in the western mountains.

of attachment of the pinnae to the rachis as well as the ratio of pinnule length to width. Taxonomists are not in agreement as to their placement and the details are botanical rather than horticultural. Superficially var. latiusculum is from eastern North American and has a sparsely hairy undersurface. Var. pubescens is from the west and reputed to have a denser undercoat of hairs. Like Equisetum, var. pubescens was a pioneer plant on the devastated barrens of Washington State's Mount Saint Helens after the 1980 volcanic eruption. It is not a welcome addition anywhere and especially in forests, as the dried autumn fronds are a serious fire hazard.

Pteridium esculentum (fit to eat—while this is the official derivation, please be careful) is an Asian species with concentrations in New Zealand and Australia. Although tall and aggressive, it bears attractive tripinnate pinnae with atypical linear pinnules of such distinction from the western species that it is not immediately recognized as bracken. It is, however, still a weed.

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