The National Park has 75% of the valley mires in north-western Europe (90 out of 120).
The permanently waterlogged soils along many of the valley sides and bottoms has led to the formation of the most important mire system in Western Europe supporting plants such as mosses, bog asphodel and white beaked sedge. Dragonflies and damselflies abound.
When soils become waterlogged, organic matter no longer breaks down but accumulates as peat. As the peat builds up, plants of bogs and mires begin to grow. In the New Forest most mires are found in the valleys, often towards the south of the Park. A valley location means that water feeding the mire will have passed through the surrounding rocks and soils and be relatively rich in nutrients.
The water movement through the mire creates complicated patterns of nutrients and vegetation. At the outer edges of the mire sphagnum mosses are commonly found alongside different orchid species, cotton grass, sundews and bladderworts. This is the most nutrient poor soil on the mire. Plants such as sundews and bladderworts thrive here as both are adapted to low nutrients by being carnivorous on small insects.
Purple moor-grass and bog myrtle are found towards the middle of the mire along with areas colonised by alder and birch trees.
This last zone often has many other plant species associated with it. Mires are generally rich in plants with over 150 species being recorded on the better sites.