Bracken BNG Units
Low
Grassland
Trusted by Developers and Landowners
What is Bracken?
Bracken-dominated grassland is a habitat formed where bracken fern (Pteridium aquilinum) becomes the principal vegetation cover. Bracken is a native fern species that has long been part of the UK’s semi-natural landscapes. It dies back in autumn, lies dormant in winter, and regenerates each spring from a widespread and nutrient-rich rhizome system.
Bracken is classified as a grassland habitat that is widespread, persistent and strongly competitive.
Why It Matters for BNG
Bracken mosaics supply limited but usable biodiversity units where higher value habitats are not feasible. They contribute structure within wider site strategies.
Land dominated by bracken can be registered for BNG units with minimal intervention. Natural spread and light management meet classification requirements.
Where Are They Found?
Bracken habitat is common in upland and some lowland grasslands. It occurs across most of the UK except marshes or bogs and is typical on hillsides, woodland clearings, moorland and acid grassland.
Soil & Site Requirements
Bracken grows best on well drained, deep, acidic soils with a pH between 3 and 7.6. It is most vigorous below pH 4.5. It avoids waterlogged ground and performs well on productive brown earths in both exposed and shaded locations.
How New Bracken Habitat Is Created
Inputs
• Cease grazing to allow bracken rhizomes to expand without disturbance
• Stop cutting and mechanical control
• Allow natural colonisation through rhizomes and spores
• Reduce competition from grasses and scrub on suitable acidic soils
• Avoid fertiliser or soil improvement, as nutrient enrichment suppresses bracken dominance
Management
• Leave the site unmanaged to encourage bracken spread
• Maintain open conditions where rhizomes can extend laterally
• Avoid interventions such as cutting or repeated trampling that would weaken the stand
Landscape
• Establish bracken on open acidic hillsides, clearings or abandoned grassland
• Allow natural expansion from neighbouring bracken stands
• Position creation where bracken already occurs locally and conditions favour rapid dominance
How Existing Bracken Habitat Is Improved
Inputs
• Reduce bracken density through light cattle or pony grazing
• Break up accumulated litter to open the sward
• Use cutting, burning or mechanical disturbance where appropriate
• Support re vegetation by reducing shading and enabling ground flora to establish
Management
• Apply grazing in spring and summer to disrupt rhizomes and suppress dominance
• Remove dense litter layers to allow light to reach the ground
• Control bracken where it prevents more diverse grassland flora from returning
• Plan management to create gaps for species such as heath bedstraw or violets where present
• Recognise that within BNG, bracken remains a Poor condition habitat even with management
Landscape
• Restore adjacent land where bracken cover can be reduced to reconnect grassland areas
• Improve site resilience by breaking up large monocultures and creating more open mosaics
• Use management to shift some bracken dominated areas back toward more diverse grassland
• Support ecological connectivity by reducing continuous dense bracken where feasible
Target Condition
Bracken habitat in its defined BNG condition should:
• Be dominated by bracken fern (Pteridium aquilinum) with over 95 percent canopy cover at peak growth
• Hold a fixed Poor condition rating under the Biodiversity Net Gain metric
• Show minimal ground flora due to suppression by dense bracken and accumulated litter
• Indicate limited management, where lack of intervention allows bracken to maintain dominance
• Occur only where bracken is the primary cover and not under woodland canopy or mixed habitats
The BNG Value of Bracken
• Distinctiveness: Low
• Condition Potential: Fixed at Poor, with no pathway to higher condition within the BNG metric
• Habitat Connectivity: Provides limited connectivity benefits, offering cover for wildlife but restricted species richness
• Climate and Landscape Context: Functions as a baseline habitat where alternative grassland options are not feasible, with enhancement opportunities remaining highly constrained
Species Typical of Bracken
Canopy or Primary Layer
• Bracken fern (Pteridium aquilinum)
Shrub or Secondary Layer
• Occasional bramble
• Occasional gorse
• Sparse scrub where present
Ground Flora or Understorey
• Heath bedstraw
• Violets
• Fine grasses in open patches
• Mosses
• Scattered ferns where cover is lighter
Frequently Asked Questions
What is Bracken?
Areas dominated by continuous or near-continuous cover of Bracken (Pteridium aquilinum). While it can provide cover for some species, extensive stands reduce biodiversity.
How is BNG measured here?
It scores a low distinctiveness and condition in the metric. Its value is generally minimal unless it covers a sensitive archaeological site or is part of a desirable mosaic.
How can I achieve BNG?
BNG is usually achieved by Conversion (a high uplift) of Bracken into a higher-value habitat like Heathland, Acid Grassland, or Woodland.
What is the BNG target condition?
The target is to reduce Bracken cover significantly to allow other, higher-value species to establish, thus converting the habitat type.
What management is required?
Management is challenging and often requires chemical treatment, rolling, or controlled grazing over several years to suppress the rhizomes and allow other vegetation to establish.
Exploring Other Habitats?
Arable Field Margins Pollen and Nectar
Arable field margins pollen and nectar are grass margins around arable fields sown with wildflowers and legumes managed specifically to provide pollen and nectar resources for invertebrates. The mix must include at least four nectar-rich flowering species and the margin is kept low-input and rotationally cut to maintain flowering through the season. The arable field must remain in a crop rotation including an arable crop.
Unlike wild bird seed margins, the management objective here is flowering continuity for pollinators rather than seed retention for birds. This habitat type sits within the Cropland broad habitat in the BNG metric and is classified separately from tussocky margins, cultivated margins and game bird mix.
Arable Field Margins Game Bird Mix
Arable field margins game bird mix are margins, strips, blocks or corners around arable fields sown with wild bird cover crops and left unharvested over winter so that seed produced by the plants remains available to farmland wildlife. The arable field must be in a crop rotation that includes an arable crop, such as wheat, barley, maize or oats, even if in certain years the field is in temporary grass, set-aside or fallow.
Mixes typically combine seed-bearing cereals, brassicas and oil-rich crops to provide food through the winter hungry gap and standing cover for gamebirds and declining farmland bird species.
Arable Field Margins Cultivated Annually
Arable field margins cultivated annually are strips along the edges of arable fields, typically 2–12 metres wide, managed under a low-input regime to support annual arable plants. They are lightly cultivated each year, usually in late summer or autumn, without herbicide or fertiliser, creating the open, disturbed soil conditions that annual arable flora requires to germinate.
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