The warmer climate also brought vegetation and over the years large areas of Northumberland became covered with great forests. The Ouseburn valley became covered in a dense forest of oak, ash, holly and hazel and this tree selection can still be seen today, particularly near Castles Farm Bridge at the North end of the Dene, although other species are intermixed. It would have remained a quiet wooded valley for thousands of years and been populated by bears, beaver, wolves and wild boar.During the last several hundred years, improved farming methods and the beginnings of industrialisation began to see some woodlands being cut down to satisfy the growing demand for timber and farmland, especially where the landscape was relatively flat and accessible.
It is probable that the steep sided valley we know as Jesmond Dene has always been wooded, but gradually, industries crept in and by the 19th century the Dene was home to watermills, various quarries and pits and an iron foundry. Prior to the mid 1800s the woodland was probably more straggly than today and interspersed with a heavy undergrowth of gorse, brambles and the like.
In the 1850s William George Armstrong (later Lord Armstrong) the armament manufacturer, (later Lord Armstrong of Cragside, Northumberland) bought up large areas of the valley. With his wife, he enclosed the land and transformed it into the landscaped parkland that we know today. With his fascination for water it is no surprise that he altered the river. A large waterfall, weirs and rock islands were created near to the mill, along with several bridges including the one from which to view the waterfall, and a network of footpaths. The waterfall is the biggest alteration to the river and was a result of blasting out the river bed downstream, while building up the area upstream. He also had a bridge installed to enable viewing of the waterfall. They additionally introduced exotic non-native species of trees and shrubs such as cedars, junipers, Californian Redwoods and the rhododendron.
