Hawthorn Dene Nature Reserve

We all enjoy celebrating birthdays, so we thought we should recognise the 60th anniversary of Hawthorn Dene becoming a Durham Wildlife Trust nature reserve.

Although we are celebrating a 60-year association with Durham Wildlife Trust, Hawthorn Dene has, of course, been around for much longer than that. In Hawthorn Dene’s life, 60 years is very much recent history – what makes the site so fascinating happened millions of years ago. Hawthorn Dene is sited on an outcrop of the Durham Magnesian Limestone Plateau, which was formed 270 million years ago. At that time, the Zechstein Sea flooded the area, depositing minerals rich in magnesium and calcium, above layers of organic material that formed the coal that became the basis of County Durham’s mining heritage. Although the Hawthorn Burn trickles through the site, this could not have formed the Dene. Glacial meltwater carved out the Dene, enlarging a fault in the relatively soft limestone, eroding the rock, and thus forming the steep sides that are characteristic of the denes along the Durham coast. The underlying geology and steep sides have shaped the woodland habitat we see today, providing protection from the harsh winds and mining activity. The result is that, today, Hawthorn Dene is one of the most extensive, diverse and least disturbed areas of woodland on the Durham Magnesian Limestone Plateau.

Hawthorn Dene is classed as an ancient woodland, which means that it has existed continuously as a woodland since at least 1600AD. Th is is evidenced by the presence of certain species, like wood anemone, which primarily spread via rhizomes (a creeping underground stem). These plants spread slowly, in the case of wood anemone at a rate of approximately six feet every 100 years. So next time you are out in Hawthorn Dene and you see a carpet of these flowers, stop to have a think about how long they took to grow. 

Originally purchased from the Pemberton family in 1965, the acquisition of the site pre-dates the establishment of what we know today as Durham Wildlife Trust, which was formed in 1971. Before that time, there was a joint Durham and Northumberland Wildlife Trust stretching from the River Tees to the Scottish border. Within the site, many historical landmarks can still be seen – although virtually no sign remains of Hawthorn Towers, the former Pemberton Family home – which fell into disrepair before finally being demolished in 1969. Two lime kilns can be seen in the northern plantation, which were likely used to make quicklime to fertilise agricultural fields. There are even the remains of a private railway station that once served Hawthorn Towers when it was still in use, in the early 20th Century.

During Durham Wildlife Trust’s stewardship of the site, (SSSI) in 1968, due to the diversity of the woodland species. Many uncommon species are present in the woodland, such as herb-Paris and bird’s-nest orchid, in addition to many of the ancient woodland indicator species. To the east, near the former site of Hawthorn Towers, lies a species-rich magnesian limestone grassland, which is part of the separate Durham Coast SSSI designation for coastal magnesian limestone grasslands.

Our management of the Dene, although only a brief part in its overall lifetime, has primarily focused on protecting these ancient features. Within the woodland, we coppice hazel stands, opening up the canopy so pockets of sunlight can reach the woodland floor and encourage woodland plants to grow. Invasive or non-native species, like Himalayan balsam, are removed, and sycamores – which can dominate the canopy and woodland floor – are rotationally cleared, ensuring space is available for other species within the site to thrive. The meadow is cut annually after the flowers have set seed, ensuring that wildflowers will bloom the following year.

Trimdon Grange Quarry

In addition to Hawthorn Dene, we are also celebrating the 50th anniversary for Trimdon Grange Quarry. Although the landscape formation differs from Hawthorn, in that it wasn’t formed by glacial meltwater, this site shares the underlying geology of the Durham Magnesian Limestone Plateau formed 270 million years ago. An area of Trimdon Grange Quarry was also designated as a SSSI in 1992 for its geological features and the nationally rare magnesian limestone grassland habitat. An estimated 270 hectares of magnesian limestone grassland remains within Britain, with 177 hectares of this located within County Durham. This demonstrates the importance of these limestone sites not only for the region, but for Britain as a whole.

At Trimdon, the meadows are cut annually to ensure that natural succession does not take place, with encroaching woody species from the woodland pushed back to the edges. This prevents the coarser vegetation from shading out, and out-competing, the more delicate meadow species.

Elsewhere on the reserve, we have areas of ash and hawthorn woodland with patches of dense scrub. These woodland features are managed through rotational coppicing within the woodland to create a mixed-age structure, and open up pockets of light into the understory. It really is a privilege to be the stewards of these wonderful sites, and to celebrate these milestones. I know I’m looking forward to many to come.