How to Rewild

Bracken

Habitat Management Plan

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Bracken
Habitat Guide

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Bracken is an ecosystem engineer, shifting the conditions within a habitat, enabling this one species to form a near-monoculture on many Acid Grassland sites.

Sub Habitats

Grassland habitats dominated by the perennial fern, Bracken, which shades out other vegetation and deposits nutrient-rich leaf litter.

How to Identify Bracken

Perhaps our most recognisable fern, Bracken (Pteridium aquilinum) is an annual plant, growing afresh every year, with ‘shepherd’s crook’ new growth appearing through grassland in May. The plant then grows rapidly, putting on over a metre, and potentially 1.5m through the growing season, creating a low canopy of fronds that turn orange-brown in the autumn before shrivelling and collapsing over winter.

Bracken dominated hillside
Bracken may dominate entire hillsides, as it does here on Sugar Loaf Mountain in the Brecon Beacons

Whether to Control Bracken

Whether or not to control Bracken is a complicated issue. This plant is a native species, which typically dominates Acid Grassland ecosystems – these landscapes are arguably an artefact of upland sheep farming. It may also be frequently found in woodland. Bracken appears to be significantly less of a problem in areas where cattle are grazed, as the larger animals trample this plant underfoot, while sheep do not.

However, Bracken is able to modify the conditions of Acid Grassland over time, and its presence reduces the diversity of wildflowers and grasses. The plant fixes nitrogen in its roots, which enriches the soil, and allows it to put on such extravagant growth in so short a growing season. The resulting leaf litter is so prolific that it chokes plant life beneath, preventing a healthy ground flora from thriving alongside Bracken. The fern also produces chemicals that render the soil toxic to other species of plant, helping it to maintain a near-monoculture.

Nevertheless, in degraded Acid Grasslands, Bracken may be the only tall vegetation around, creating much-needed structural diversity. It can provide shelter from harsh conditions, and is an essential refuge for Adders, which rely heavily on this unique habitat. The tall perches are used by birds and leaf litter mulches the ground, mitigating erosion from livestock and walkers.

Alongside the issue of grassland dominance, there is some evidence that consuming Bracken, and soil which it grows in (though why you would do this is unclear) can cause the development or worsening of certain cancers. This is more of an issue in cattle and other livestock in close contact with the plant. 

Potentially of more concern to humans is that Bracken is a perfect habitat for ticks, especially when there is an overpopulation of deer. The humid, shady conditions prevent the nymphs from drying out while they await a new host. Ticks are increasingly likely to carry Lyme disease in the UK, which has long term health implications.

How to Control Bracken

One of the most effective means of controlling Bracken has recently been banned in parts of the UK – ‘Asulam’ – a herbicide with potentially toxic effects. Asulox is the same product under another brand name, and this is banned for use in Scotland and Wales, though it was still permitted under emergency authorisation in England in 2023.

Any kind of control measure has risks – mechanical control of bracken crushes reptiles and mammals sheltering in the leaf litter; manual cutting is dangerous in areas with Lyme disease; chemical control can have toxic effects beyond the intended target plant. Control strategies that aim to eradicate the Bracken entirely are likely to reduce overall diversity in the ecosystem.

When it comes to control measures, there are a number of different options available. Though cattle grazing is perhaps the most ecologically-sound, it isn’t without risk, as Bracken is toxic to livestock.

Cutting is a method that requires sustained effort over the long term, and is not a permanent solution, as stopping the treatment will result in Bracken returning rapidly. The plants can be cut twice per year, in mid June and then again in late July. This slowly reduces the store of energy in the plant’s roots, but a sparse population of Bracken will persist unless the ferns are cut once fortnightly for 3 years or more.

Rolling or bruising of Bracken is a mechanical control measure carried out with either horse-drawn or tractor-drawn rollers. In sensitive habitats with threatened species inhabiting the leaf litter, this should be carried out only in moderation, leaving refuges for reptiles. In late summer and early autumn, this method is more likely to kill basking snakes. At any time of year, it could reduce the structural diversity of the habitat, as scrub may also be damaged. However, after a few years of rolling once annually, especially if paired with cattle grazing, Bracken is likely to become very sparse.

Remote-controlled mulchers are now available, which can be funded under government schemes and may be preferable for land inaccessible to heavy machinery.

Cutting, then spraying with herbicide is a far more effective treatment, requiring less work for better results. However, with the selective herbicide Asulam coming off the market in much of the UK, and alternatives like Roundup having significant impacts on the ground flora, soil biota and, potentially, human health, it is difficult to recommend this strategy for dealing with what is in fact a native plant.

If you are already registered with a national agricultural payments scheme, funding is likely to be available for Bracken control.

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