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A class of ferns, brackens are one of the oldest known plants, with fossil specimens dating 55 million years. It is one of most successful, widespread plants, absent only in dry deserts and the continent of Antarctica. Derived from the Scandinavian word for “fern,” the common name is reserved for the plant family Dennstaedtiaceae. At one time, they were broadly classified in the genus Pteridium, but they are identified in about ten different genetic species.
Brackens are characterized by their large triangular, and highly articulated leaf structure, called fronds. Each can grow to more than 8 feet (2.4 meters) long. The plants are correspondingly large, from around 3.3 to 9.8 feet (1 to 3 m) tall. Their primitive vascular stems can measure 0.4 inches (1 cm) in diameter. Also characteristic, the fronds develop as tight curls of plant tissue that unfurl and expand to mature size.
Like most ferns, a bracken is a perennial herbaceous plant. It lacks the tough cambium tissue of woody plants. Unlike annuals, which die each growing season, brackens’ reproductive cycle dictates that they survive two or more years. In alternating years, they reproduce both sexually and asexually. Two gamete cells with identical chromosomes, sperm and ovary, fuse, and the following year multiply into single-celled spores lining the underside of fronds, to be distributed by wind.
The spores propagate underground as a rootstock called a rhizome. Individual plants shoot from this root. Environmentally, brackens serve as a low canopy for creatures and plants that benefit from the extra cover and shade. Ecologically, they are food for many insect larva. Uncontrolled, they are an aggressive and invasive plant.
Part of brackens’ extraordinary evolutionary success is their secretion of allelopathic chemicals. The complex compounds, released into surrounding soil, are toxic and inhibit the germination of other competing plant species. Some of these chemicals are potentially natural insecticides and herbicides.
Brackens are also food for humans. The delicacy commonly called fiddleheads, eaten either raw, cooked, or pickled, are the plant’s curled immature leaves. Their rootstock is used to brew beer; also dried and ground to a starchy flour. In Japan, the flour is baked into cakes and confections. In Korea, fiddleheads are steamed with rice into the common dish called bibimbap.
The ferns were a staple for native Maori of New Zealand, and brackens have been used as an herbal remedy against parasitic worms of the digestive tract. Ingested brackens, however, are a proven carcinogen in some laboratory animals, perhaps because of their spores. Consumed raw in excess, they can cause a condition commonly called beriberi, an atrophy and paralysis of the body’s nervous, circulatory, and digestive systems. Although studies have proven inconclusive, even cooked and moderately consumed plants are suspected agents of fatal stomach cancer.