… and A Little Help from Our Swedish Friend, by Kirsty Pollard – Heart of Durham Conservation Officer
If someone asked you what is the most common plant in the world, what wold you reply? Some botanists believe that, among the vascular plants, this title should be awarded to none other than our native Pteridium aquilinum, more commonly known as bracken. Bracken is found on every continent – bar Antarctica – and can survive at sea level and as high as 3,000m above.
Fossil records indicate that bracken, and other fern species, date as far back as 55 million years ago; 200 million years before the first flowering plants emerged. Bracken’s lack of flowers- and subsequent seeds- baffled early scientists as they pondered how these plants were capable of propagating. The apparent invisible nature of bracken seeds gave birth to the folklore: whoever held the tiny spores of bracken in their hands would become as invisible as the seeds. We now know, of course, that the bracken seeds are seemingly invisible because they don’t exist and that ferns, instead, produce spores which are carried off by the wind. In actual fact, the spores are relatively unsuccessful and the bracken has a more powerful means of achieving its course to landscape-scale domination. Beneath the soil, horizontal stems called rhizomes are at work. Rhizomes can spread over 120cm in one year, allowing new shoots and root systems to develop some distance from the original plant. The rhizomes can be at depths of up to 100cm below the surface making bracken a resilient plant and difficult to remove once established.
Above the ground, bracken leaves (or fronds) unfurl in a graceful manner to reveal an alternate pattern of fronds feathering the stem. It is perhaps this delicate, annual unfurling which has led to a number of myths that bracken has the ability to grant perpetual youth. But before you rush out and start slathering bracken all over your skin, be warned! Cut or damaged bracken produces hydrogen cyanide toxin, the plants defence mechanism to deter browsing animals.
The lack of willing native grazers, coupled with changes in land use- such as the reduction of large trampling herbivores- allows bracken to quickly invade and dominate huge areas of the landscape, outcompeting other valuable native plants. For this reason we actively control bracken and encourage a greater diversity of species and microhabitats. Pow Hill Heath is an example of how bracken is dominating a sensitive and valuable area of lowland heath habitat. In partnership with Northumbrian Water, our Heart of Durham Volunteers have been bashing and trampling the bracken for several years at this site, a control strategy which results in a gradual reduction of bracken density. But when it comes to bracken control, four legs are better than two which is why we recruit the assistance of ‘Orli’; a North Swedish breed of horse who, with assistance of an experienced handler, pulls a bespoke bracken roller across the heath crushing the bracken stems as he goes.
It may not be immediate gratification but we are seeing this hard work begin to pay off; as the bracken becomes weaker and less dominating, heathers, bilberry and other heath species return. These ‘glades’ among the bracken provide basking areas for adders and feeding opportunities for species such as heath bumblebees.
We look forward to seeing how the heath recovers as the bracken becomes less dominant.
And in the meantime, our volunteers can have a well-earned cup of tea…. and a polo-mint for Orli.