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
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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?
Open Mosaic Habitats on Previously Developed Land BNG
Open Mosaic Habitats on previously developed land are brownfield sites where disturbance, bare substrates, and early successional vegetation create a structurally diverse mosaic. The habitat supports specialised flora and invertebrates that depend on skeletal soils, bare ground, and pioneer plant communities.
The mosaic typically includes bare ground, ephemeral and short perennial vegetation, flower-rich open grassland, scrub patches, and occasional wet features.
Willow Scrub
Willow scrub is a transitional habitat dominated by native willow species, typically grey willow and goat willow, often with hawthorn, hazel, and dog rose. It forms in damp ground, at woodland margins, or on disturbed sites where scrub colonises freely.
The Willow scrub habitat is characterised by a mosaic structure: scrub cover between 10 and 60 percent with open grassland, wetland, or bare ground filling the gaps. A varied age structure, from seedlings to mature stems, supports higher condition scores. Ground flora is diverse where scrub remains open and light levels allow herbs and grasses to persist.
Upland Hay Meadow
Upland hay meadows are species rich grasslands dominated by a mix of fine grasses and abundant herbaceous wildflowers such as sweet vernal-grass, wood crane’s-bill, great burnet, pignut, and lady’s mantles.
These meadows have developed through long term traditional management that combines light grazing with a late summer hay cut. Rare species including lesser butterfly-orchid and burnt orchid are sometimes found.
This habitat is a dense mix of grasses and a wide variety of wildflowers, with no single grass species dominating the vegetation.
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