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
For Developers
For Landowners
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
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, reflecting modest ecological value compared with other grassland types
• 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
Exploring Other Habitats?
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.
Upland Calcareous Grassland
Upland calcareous grassland is a springy, species-rich habitat occurring above approximately 250–300 metres on lime-rich, or “base-rich,” soils. The habitat develops as a short, species rich sward of calcicolous grasses, herbs and orchids adapted to alkaline conditions and cooler upland climates The grassland appears patchy and open, with fine grasses, colourful herbs and scattered rock outcrops. Wild thyme, common rock rose and bird’s foot trefoil often grow alongside sheep’s fescue and upright brome, creating a varied mosaic.
Upland Acid Grassland
Upland Acid Grassland is a mix of fine grasses, mosses and small herbaceous plants adapted to low pH and limited nutrients. This habitat appears as an open grassy landscape, often dominated by mat grass or purple moor grass. Texture and color come from all patches of tormentil, heath bedstraw and scattered mosses.
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