Durham Wildlife Trust’s Heart of Durham Project works in partnership with Northumbrian Water to manage areas around Derwent Reservoir to enhance biodiversity.

 Pow Hill Heath borders the south side of the reservoir and is a mid altitude heath, which is a scarce habitat. The site was awarded Country Wildlife Status in 2000, because although small, it is an important area of unimproved acid grassland which supports a range of plants, reptiles, birds, mammals and invertebrates. The characteristic flora of a mid altitude heath is heather, bilbury, wavy hair grass, common milk wort, louse worts, stichworts, marsh thistles, harebell, tormentil, cotton grass and speedwells as well as many more.

At Pow Hill heath, the inundation of bracken over many years has become a problem, shading out this very important remnant heathland flora and the mild and wet winters of recent times have proved to be the perfect conditions for bracken to thrive. Northumbrian Water and the Heart of Durham Project have tried numerous management options, from grazing with Soay sheep who were introduced to the site to nibble the young fronds of bracken as they emerged from the soil early in the spring, to flailing with a quad bike. Despite this treatment bracken at this site in certain places was growing to over 5 feet tall!

Soay sheep originally from the Western Isles of Scotland where introduced to to Pow Hill Heath to nibble on the young bracken fronds

In 20016 a new form of attack was put into action.

The attack took the form of a programme of bracken rolling. Using a heavy metal roller drawn by a horse, the bracken is bruised, the stems bleed sap and the rhizome, the food store house of the plant, is stimulated into putting out fresh new growth. This fresh new growth depletes the rhizomes, the food store, underground. If this is done twice in a year, the bruising can deplete the store quite considerably, with the result that the growth of bracken is inhibited and becomes less vigourous. It is worth mentioning here that 90% of the bracken plant is underground in the structure of these rhizomes!

A new bracken frond looking like a Bishop’s Crook

So in 2016, in early June, when the emerging bracken started to look like a Bishop’s crook the first rolling took place, with a second rolling taking place six weeks later in mid July.  2017 is the second year of using this bracken rolling regime and the results are beginning to show.

A specially adapted heavy metal roller, pulled by a horse, crushes the fronds of bracken.

August 2016 -The second rolling of the bracken for the year. Note the height of the bracken compared to the height of the horse.

2016 second rolling

Compare the height of the bracken at the time of the second rolling this year (2017)

2017, view across the reservoir towards the dam

It takes  four days to roll the whole site as Pow Hill Heath has many gradients and slopes but the heavy horses are well adapted to this kind of terrain, and it is a cost effective, efficient and environmentally friendly way to manage the growth  of bracken at this site. Northumbrian Water and Durham Wildlife Trust’s Heart of Durham Project are really pleased with the results and will continue to use this method in subsequent years, whilst monitoring the growth and condition of the heathland flora such as bilbury, heather and other heathland plants.

Thank you to Chris Wadsworth from the British Horse Loggers Association and Mark Turnbull for their skill and expertise.