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Japanese Knotweed (Fallopia japonica)
A prodigious invader which is very difficult to remove. This species was introduced to Britain in the 1800's as an ornamental plant. The plant spreads slowly via rhizomes which are situated underground, new growth stems from the rhizomes and has the ability to make its way through tarmac and other manmade substances. The smallest fragments of stem and rhizome from this plant have the ability to develop into a fully grown plant. For this reason it is important to ensure that plants are never removed from the ground or broken up. The most common method of Japanese Knotweed removal is spraying or inoculation with herbicide. This is a costly process and requires and requires a number of permissions. It is also time consuming, as effective control of this species requires retreatment for around three years before the plant is totally killed. Mechanical removal of this species is also possible but stringent controls must be in place during removal and all removed plant matter must be sent to a registered landfill for safe disposal.
Japanese Knotweed foliage
Dense thicket of Himalayan Balsam
Giant Hogweed (Heracleum mantegazzianum)
Similarly, this species was introduced to Great Britain in the 1800’s. This species is unmistakable, Giant Hogweed grows to around 3 metres tall with large flowers and leaves. Seeds which are released by the plant have the ability to remain dormant in the soil for a number of years. The species presents a significant risk to human health as its sap contains furanocoumarins which causes the skin to become photosensitive leaving it susceptible to burning under Ultraviolet radiation. Under no circumstances should the removal of this plant be undertaken without the correct personal protective equipment. The main method of removal for this plant is the application of herbicide, however the removal of flower heads from the plant is also effective as it prevents the expansion of the seed bank.
Invasive Non Native Species (INNS) pose a great threat to the Wyre Catchment. Left to their own devices certain INNS would outcompete native plants and animals.
There are many varieties of INNS, fortunately the Wyre Catchment is not home to all of them but there are a number of INNS which prevail in the Wyre Catchment.
Dense stand of Japanese Knotweed
Himalayan Balsam in flower
Himalayan Balsam (Impatiens glandulifera)
Another product of Victorian horticulture, this species was introduced to the UK in the 1800’s and rapidly colonised due to its seed dispersal mechanism. This species is vigorous and will often shade out other native species to their demise. The control of this species is comparatively easy but is time and energy intensive. Removal of Himalayan Balsam is often undertaken by large groups of volunteers who remove it by hand or with small tools such as scythes. This should only be undertaken before the plant has flowered. Another common method of removal is by application of herbicide which is sprayed onto young plants before they flower.
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