As we head towards May, the great showy purple rhododendron flowers start to be seen in parks and gardens alongside their smaller cousin the Azaleas. In ornamental gardens, the towering bushes of red, pink and white provide a backdrop to immaculate clipped lawns and the first flush of flowers in the herbaceous borders. The name Rhododendron is derived from the ancient Greek and means Rose Tree.
Rhododendrons first came popular in the mid- 18th century when there was a growing fashion for woodland gardens. Many Victorian landowners were attracted to the abundant purple flowers and rapid growth of rhododendron x superponticum which they used to create cover for their shooting estate. Large areas of Castle Eden Dene were also planted with rhododendron by the Burdon family and used to edge the paths and carriage ways they created through the Dene in the early 19th century.
rhododendron x superponticum
But now nearly 200 years later, rhododendron in Castle Eden Dene is a problem. Now managed as a National Nature Reserve to showcase its fine yew and beech woodland, rhododendron plants smoother the woodland’s rich ground flora impacting on plants such as bluebells, primroses and wild garlic, and the insects and woodland butterflies which depend on them. Rhododendron bushes grow very tall and its thick inter-laced impenetrable branches means that very little lights is able to reach through its thick canopy. Its thirsty roots will leach most of the water and nutrients from the soil leaving it dry and barren. The waxy leaves of these plants are also poisonous to any animal which consumes them. Rhododendron can also be host to disease (phytophthora ramorum) which affects and kills larch and yew trees. One of the challenges for controlling Rhododendron is that it spreads quickly; a horizontal branch which touches the ground will quickly root and Rhododendron flowers produce masses of tiny seeds are easily spread.
During the past 30 years or more efforts have been underway to reduce the abundance of rhododendron across the Dene and restore the woodland habitat. The team, supported by our volunteers, have cleared large areas of Rhododendron. It requires the bushes to be cut down to ground level, leaving just a stump, with all the branches removed off site to be burnt. During the winter months herbicides are applied to the stumps to kill the remainder of the plant. The toxic layer of humus (the remains of old rhododendron leaves), is also removed to help support natural regeneration of the woodland. It takes time for areas once covered in Rhododendron bushes to recover; the team regularly check for rhododendron seedlings, and as the areas begin to recover plant young oak samplings and other native species.