Invasive and Non-native Species Recording

We are inviting the public to record their sightings of some key Invasive Species

Invasive and Non-native species or INNS are plants or animals which have been introduced (intentionally or unintentionally) to an area or habitat outside of their natural range. The introduced species can cause problems for native species such as predation, competition, introducing diseases and altering habitats. In 2010, the impacts of INNS were estimated to cost the UK more than £1.8 billion per year (more info here).

In order to reduce the spread of INNS and to target effort, we need to know where they are! We are asking you to help record 6 Invasive Non-native Species below!  Click on the photographs to record your sightings.

Have you seen these species?

New Zealand Pigmyweed

Himalayan Balsam

Japanese Knotweed

Parrots Feather

Skunk Cabbage

Winter Heliotrope


Scroll down for more information!

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New Zealand Pigmyweed (Crassula helmsii)

Australian swamp stonecrop (Crassula helmsii) is an invasive aquatic plant that dominates still and slow-flowing waterbodies. It was initially introduced from Australia in the early 1900s as a garden pond plant but is now spreading across waterbodies in the UK and parts of Western Europe.

It is particularly problematic in sensitive aquatic habitats where it has the potential to outcompete native flora and reduce oxygen levels by forming dense, impenetrable mats. This weed can also have negative impacts on recreation and can block filters necessary for water treatment. Australian swamp stonecrop tolerates extreme environmental conditions and, as such, management can be very challenging and often unsuccessful, especially for infestations in areas of high conservation value. (source)


Himalayan Balsam (Impatiens glandulifera)

As its name suggests, Himalayan balsam is from the Himalayas and was introduced here in 1839. It now an invasive weed of riverbanks and ditches, where it prevents native species from growing.

Himalayan balsam was introduced as a garden plant in 1839, but soon escaped and became widely naturalised along riverbanks and ditches, especially close to towns. It is fast-growing and spreads quickly, invading wet habitat at the expense of other, native flowers. Its explosive seed pods aid its spread by sending the seeds into the river, causing further dispersal downstream.
Our largest annual plant, it flowers from July to October. (source)


Japanese Knotweed (Fallopia japonica)

Japanese knotweed (Fallopia japonica) is native to Japan, Taiwan and northern China, and was introduced to the UK in the early 19th century as an ornamental plant. It is a perennial plant, growing each year from its extensive underground rhizomes, and spreads rapidly both by natural means and as a result of human activity.

Japanese knotweed is spread by fragments of rhizome or stem being transported to new sites. Very small fragments of stem/rhizome can give rise to new plants. The plant forms dense stands, outcompeting our native vegetation and causing nuisance and structural damage.

For more information, including what NOT to do if you find Japanese Knotweed on your property please go here.


Parrots Feather (Myriophyllum aquaticum)

Parrot’s feather (Myriophyllum aquaticum) is a distinctive perennial aquatic plant with a feather like structure, native to south and central America.  The plant was first brought to the UK in the 1870s as an aquatic plant to aerate garden ponds. After being discarded, it found its’ way into the wild; it was first recorded in the UK associated with a pond at Lingfield in Surrey in 1960.

Parrot’s feather spreads via fragmentation and is capable of forming dense infestations in suitable habitat, occupying the water column in water. The primary impact of the parrot’s feather is shading out other aquatic plants, it can also damage the invertebrate communities associated with these.

Dense growth of parrot’s feather can cause flooding and ponding of water, leading to increased health hazards, although these are not likely to be a serious problem in the UK.

Parrot’s feather could be considered a threat to tourism, angling, boating and other recreational pursuits, and hydro-electric power stations, which would result in an economic impact. (source)


American Skunk Cabbage (Lysichiton americanus)

American skunk cabbage was first recorded in the wild in 1947 in Surrey and was originally introduced to the UK from Western North America as an ornamental plant in 1901. Since then it has spread across Britain, particularly in southern and western areas.

Once established the plant can spread quickly. Infestations can dominate large areas and crowd out native species in important habitats such as wet woodlands. Its name is fitting as this plant has a characteristic pungent scent. (source)



Winter Heliotrope (Petasites fragrans)

Petasites fragrans is native to southern Europe and North Africa, but it has become naturalised in Britain (although scarce in northern Scotland) and in Ireland, where it is locally a common sight on disturbed roadside verges. This is a dioecious species, and RHS states that only male plants occur in Britain, so I think they must all be genetically identical clones.

This distinctive winter flowering species often forms dense patches of colour on shaded banks, woodland edges and disturbed roadside verges. The flowers appear when the leaves are relatively small, and as spring approaches the flowers decay but the leaves persist for many months. (source)