In its reference state, bracken (Pteridium aquilinum) is a pioneer species that paves the way for woodland. It is a pteridophyte that forms large stands of homogeneous habitat on the sides of valleys and along the coast. It typically prefers deeper acid soils and, being deciduous, dies back in the autumn to form distinctive bright orange-brown stands. For this reason, autumn is the most reliable time to map bracken – earlier in the summer the green fronds are less obvious on remote images.
In natural situations, if succession occurs unhindered, tree saplings will become established. However, the ground-layer under the bracken is often intensively sheep-grazed which restricts the scope for sapling survival. Bracken can also persist as woodland edge species that spreads out into adjacent meadows.
Because of its competitive properties, bracken is almost always considered negatively by farmers – as it reduces the area of land available to grazing stock. Nature conservationists can also view it negatively, depending on their interest area, e.g. heathland enthusiasts often manage bracken to prevent it replacing the heath, while ornithologists and lepidopterists can welcome the cover it offers for breeding birds and rare butterflies.
There are several forms of bracken management employed by land managers in the UK, including burning (the most effective way to remove litter), spraying with Asulam, cutting, trampling and mowing. Conservationists prefer the last three options.