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Bracken management in the uplands

Bracken: young growth in a clearing

Image: Andy Hay

Bracken is a well-adapted pioneer plant, which can dominate large areas of moorland. Established stands occupy an estimated 975,000 hectares of open upland and heathland in the UK.

Bracken can colonise land rapidly and has the potential to expand its area by as much as 1–3 % per year. This ability to expand rapidly is at the expense of other plants and wildlife, and can cause major problems for land managers that can result in high economic loss.

Bracken colonises ground with an open vegetation structure but is slow to colonise healthy, well managed heather stands. Bracken can become a problem on almost any land, except high mountains, and land that is periodically waterlogged or cultivated. The main reasons for the recent spread of bracken are overstocking, and increased nutrification.

Key points

  • Identify and target specific areas for control, tackle advancing areas first. A large scale approach is more cost-effective than a piecemeal approach
  • Develop a long-term bracken control programme following expert advice
  • Ensure that the bracken has no high conservation value of its own before commencing control
  • Grant aid may be available from statutory conservation agencies and through agri-environment schemes

Benefits to wildlife

Management to maintain scattered stands of bracken on appropriate sites can provide good habitat for a variety of wildlife 

Bracken dominated areas may be less important for wildlife than the communities displaced by it. In many areas it is of major conservation benefit to re-establish the previous semi-natural habitat eg. upland heath. Bracken also limits the forage area available to livestock. 

However, locally bracken can be of value where it occurs mixed with other vegetation types, and smallareas should be retained in appropriate locations. In some areas, bracken can support a woodland ground flora, for example violets and bluebells, by acting as a substitute woodland canopy. Violets are the larval food plant of the high brown fritillary a rare and declining species of butterfly. 

Small stands of bracken provide nesting, feeding and roosting habitat for a variety of birds, for example ring ouzels, twites, whinchats, and stonechats. 

Implementation

Removing bracken encourages primary habitats to re-establish, which are of greater importance for wildlife.

Bracken control 

Controlling bracken is a long-term and often expensive undertaking and specialist advice should be sought.   

The expense of large-scale management is often beyond most individuals and needs collaboration of individuals and organisations. 

Where a small-scale approach is adopted, annual ongoing management is required to prevent rapid recolonisation.   

Identify key target areas, and tackle these first. Targeting the leading edge of bracken stands may slow down colonisation into bracken free areas. These should be identified and mapped by surveying bracken distribution in July to October when bracken is most visible.   

The peak time to control bracken may coincide with other wildlife activity, especially nesting birds and their unfledged young, and deer fawns. 

When planning to manage an area, survey it first for  evidence of any breeding activity by birds and other wildlife and avoid disrupting them.   

Where bracken cover encourages the growth of violet species, consider the potential occurrence of the high brown fritillary. This butterfly is a rare species in the UK and bracken control may be detrimental. 

Methods of bracken control   

Though cutting and rolling both reduce bracken vigour and encourage recovery of vegetation, they do not provide full control. Alternative methods are needed to achieve this.   

Cutting regimes     

Cutting is most effective when bracken is at, or near, full frond. This is even more efficient if bracken is cut twice in the same growing season. In many upland areas slow growth may mean two cuts is not possible. In this case a single cut, close to the ground, in mid late July can increase the potential for early frost damage to regenerating bracken and surface rhizomes.     

Annual cutting will need to be repeated until thebracken disappears, which can take in excess of 10 years in well established stands.     

Cutting once will produce an even stand with more active buds, which may increase the effectiveness of chemical treatment in the following year.     

Where ground-nesting birds are present, cutting should be avoided during May   July. Leave those areas until last or avoid until after any nests have become inactive. The period to wait is likely to be only a matter of days or a couple of weeks. If in doubt seek specialist advice.     

The use of rolling     

If cutting is not possible, consider rolling the bracken. The timing is the same as for cutting. There are a number of small machines on the market designed specifically for this type of work, which can be towed behind tractors or 4x4 vehicles.       

Rolling does not cut off the stems but leaves them attached to the root to bleed the sap, this reduces food energy for bud development in the following year.       

Each rolling operation can reduce shoots by about one third, reducing a dense stand of bracken into more scattered fronds.       

Rolling for three consecutive years has been shown to be more effective than carrying out a one-off operation. Even so, bracken control will need to continue for more than three years to avoid recolonisation.     

Grazing regimes     

Temporary mob stocking, particularly using cattle, horses or ponies in May and June, may crush emerging bracken fronds resulting in reduced bracken cover. Sufficient fodder will be required to prevent livestock eating the bracken.       

Mob stocking can damage vegetation beneath the bracken canopy. It can also lead to nutrient enrichment and damage bird nests. Where the management objective is to restore heather moorland, and other semi-natural vegetation communities, mob stocking is often inappropriate.     

Trampling also increases the rate of breakdown of dense bracken litter.       

Correct stocking levels can be critical to prevent bracken invasion. In the uplands overgrazing can reduce vegetation competition, which favours bracken spread.     

Herbicide treatment     

Herbicide treatment is highly effective if a full programme of primary treatment and aftercare is undertaken.       

Asulam is a selective, systemic herbicide known to be effective against bracken, but thought to have only low toxicity. It can be applied either as a spot treatment to individual fronds, or by using a tractor or ATV mounted sprayer. In large scale bracken control programmes aerial spraying using helicopters is a valid and cost effective option.       

The systemic nature of Asulam means that for effective treatment it should only be applied to mature fronds ensuring maximum translocation to the underground rhizomes. Fronds are normally mature from mid July to the end of August. At this time most birds should have completed breeding and are not likely to be affected by herbicide application.       

Glyphosate can be used to spray dense areas of bracken with no understorey.       

Where stands are more open, and there is an issue of affecting non-target species of flora, consider the possibility of weedwiping or application with a hand lance.       

The statutory conditions of use on the product label must be adhered to when using any chemicals for bracken management.     

Other management considerations     

Any bracken control programme must be completed, otherwise bracken will re-establish.       

The management of heather moorland often encourages the growth of bracken. Burning should not be undertaken in close proximity to existing stands of bracken.       

 Bracken is carcinogenic to humans, and high numbers of sheep ticks associated with bracken can increase the likelihood of transmission of Lyme disease.     

Last updated: 28 November 2008

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