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Bracken - General Information

Bracken is a problem on Dartmoor, as elsewhere. It is spreading, engulfing archaeological sites and making access difficult in some areas. It also brings the twin problems of toxicity and ticks.

One reason for its spread may be milder winters, through climate change, which cause it not to die back so much in more sheltered areas. Other reasons are less trampling by livestock and less swaling - this being the annual burning of parts of the moor to encourage new grass for grazing by livestock.

The reduction in trampling is due to there being fewer ponies on the moor, only about 2,000 now compared to 20,000 in the 1970's and many more before that. There are also fewer cattle and sheep. The economics of hill farming are such that farmers cannot afford to feed large numbers of animals through the winter. They have to survive on the hay or silage cut in the summer on their inbye fields.

As already stated, bracken brings two major health problems: toxicity and ticks. It is poisonous due to the ptaquiloside that it contains. This has a reactive cyclopropane ring that has been isolated from the fern and its potent carcinogenicity proven. It can cause several illnesses (even fatalities) in animals and may have caused gastric cancer in people in North Wales (see The fatal fern below).

The sap (or latex) of the fern also contains glycosides which are "toxins in which at least one sugar molecule is linked with oxygen to another compound, often nitrogen-based. They become harmful when the sugar molecule is stripped off, as in the process of digestion" (Source: The poison plant patch).

The toxicity problem will not be dealt with further on this web site.

The tick problem on Dartmoor will be dealt with via the link below. Suffice it to say that more bracken means more ticks: these are an increasing health risk to walkers and other users of the moor because they can harbour Lyme disease (also known as borreliosis) and other diseases. Wikipedia - Lyme_disease states that "Untreated or inadequately treated cases of Lyme disease may progress to a chronic form most commonly characterized by meningoencephalitis, cardiac inflammation (myocarditis), frank arthritis, and fatigue". They can also harbour other diseases (see the "Ticks on Dartmoor" link below).

Links to .....

• Bracken control on Dartmoor - as practised by Dartmoor Preservation Association

• Ticks on Dartmoor - describing their occurrence and associated health risks e.g. Lyme disease

Some bracken web links

• Biological Flora of the British Isles: Pteridium aquilinum (L.) Kuhn - "Pteridium is a complex genus comprising a number of species, subspecies and varieties. The treatment here is based on a recent revision that incorporates both morphological and molecular data, and is related to its geographical distribution"

• Bracken Advisory Commission - Bracken can damage your health - Quote - "It will come as a surprise to most people that bracken is one of the most poisonous plants on Earth"

• Bracken as a Peat Alternative - Quote "This has involved clearance by swiping, chemical spraying, chisel ploughing and cutting, often resulting in the production of ‘waste’ material. Cutting while green can be very effective at reducing ground cover and vigour, eventually leading to the eradication of bracken (Brown and Robinson, 1997).

• Bracken fern

• Bracken News - discussion group via list-server that you have to subscribe to (free)

• Bracken - world species list

• Carcinogenic effects of ptaquiloside in bracken fern and related compounds

• Dartmoor Preservation Association - Bracken Control Document

• International Bracken Group (IBG) ***

• Ptaquiloside - the Poison in Bracken Quote - "highly carcinogenic causing polyp-type bladder and intestinal tumours in grazing animals who ate large amounts of bracken or were fed bracken-containing fodder" ..... plus ..... Quote - "This botanical pest is considered something of a delicacy in some parts of the world. The Japanese, for instance, often dine on the young bracken sprouts known as fiddleheads (pictured) and it is considered a treat in some areas of Canada and the US too. The trouble is, bracken, while edible, is also highly toxic - especially the fiddleheads - and has been causing bellyache for farmers for centuries where unwary ruminants might graze on the succulent curling shoots ..... also ..... Quote - "Bracken poisoning causes depression of bone-marrow activity which leads to severe leukopenia - a form of white blood cell anaemia, - thrombocytopenia - an abnormally low blood platelet count - and hemorrhagic syndrome. In addition, the uncooked plant contains the enzyme thiaminase, which can destroy thiamine (vitamin B1) and cause a possibly fatal disease similar to beri-beri in non-ruminants such as horses."

• Should we be frightened of bracken? A review of the evidence

• Spray treatment of bracken Pteridium aquilinum using Asulox herbicide at Blackhill, Dorset, England - using "Asulox" herbicide. From the Conclusions - Quote "Whilst achieving short term success, it would appear that bracken has recolonised and the overall long term benefits of bracken control using Asulox are not clear. The evidence suggests that bracken management would need to be ongoing."

• The fatal fern - contaminates water supplies, causes gastric cancer, people in Gwynedd, North Wales. Last line - quote "In the meantime, don't give up drinking water but do keep trampling down the bracken when you're out for a walk."