Invasive Species
Many woodlands have become affected by invasive species of plants that can
- Affect existing tree species by preventing natural regeneration by shading
- Affect ground flora by competing, hybridising or shading out
- Present a hazard to visitors and workers
Japanese Knotweed This species is very invasive and poses enormous problems if it becomes established so it is wise to eradicate it if present. Its roots can extend down many metres, and its shoots can penetrate concrete. The only practical method for removal is repeated treatment with Glyphosate.
Himalayan Balsam This species has thick fleshy stems and attractive pink flowers. It can be particularly common near watercourses, and spreads its seeds by an unusual 'explosive' mechanism
Spanish Bluebells The Spanish Bluebell (Hyacynthoides hispanica) is a garden escapee that is becoming established in woodlands. It is larger and more vigorous than our native Bluebell (hyacynthoides non-scripta) and also hybridises with it. There is concern that it will threaten the local genetic integrity of our native Bluebell. For more information see the Natural History Museum website
Rhododendron Dealing with the presence of Rhododendron in woodlands has been an ongoing and expensive problem for many years. It was planted to provide game cover and for landscape reasons in the 19th and 20th century but has been found to prevent natural regeneration of native species through shading and its leaf litter which produces chemicals which inhibit germination. Removal is usually through clearance followed by chemical spraying of the regrowth. On the positive side the stems make good charcoal!
Snowberry Snowberry (Symphoricarpos albus) is a 1-3m high shrub with distinctive white berries which forms dense thickets in woodland. It was planted as game cover in the early 20th century.
Giant Hogweed This spectacular plant, another garden escapee, resembles our native Hogweed but can grow to over 3m high. Its sap can cause severe burns and irritation. Those dealing with it should use suitable protective clothing and gloves.
Sycamore The sycamore is a common sight within our woodlands and provides an excellent timber. In some situations, however, it can be invasive and can affect regeneration of other species because of the heavy shade and dense leaf litter. In some woodlands where it is rare or confined to a small area it might be worth trying to eradicate it, especially if the woodland is ancient.
Links
Advice on Himalayan Balsam and Giant Hogweed from the Environment Agency
Japanese Knotweed advice from the Environment Agency
Rhododendron control measures from Forest Research