NNNSI "Urban Invaders" Invasive Alien Species Survey

Humans are increasingly moving species outside their natural range, sometimes deliberately and sometimes accidentally. In the absence of their natural enemies, some species can spread rapidly and cause problems. These species are termed
‘invasive’.

Invasive non-native species are considered to be one of the most important causes of biodiversity loss worldwide, second only to habitat destruction and fragmentation.
They can also have significant economic impacts. One recent estimate put their cost at almost £2 billion a year in the UK alone!

Urban areas are a hotspot for invasive non-native plants. Urban Invaders - aims to help improve the quality of our data on some of the most damaging invasive plants found in Norfolk. We need YOU to help by telling us when
and where you see them.

THE URBAN INVADERS SURVEY SPECIES ARE:

New Zealand Pigmyweed/Australian Swamp-stonecrop (Crassula helmsii)
Floating pennywort (Hydrocotyle ranunculoides)
Himalayan balsam (Impatiens glandulifera)
Giant hogweed (Heracleum mantegazzianum)
Japanese knotweed (Fallopia japonica)
Tree of heaven (Ailanthus altissima)

Download the Urban Invaders Leaflet here

 

IF YOU HAVE SEEN ANY OF THESE 6 NON-NATIVE SPECIES PLEASE USE OUR ONLINE RECORDING FORM (LINKS BELOW) TO TELL US ABOUT YOUR SIGHTING(S).

FOR MORE INFORMATION ON EACH OF THESE SPECIES SEE DETAILS BELOW THE ONLINE RECORDING FORM LINKS.



HAVE YOU SPOTTED ANY OF THESE 6 NON-NATIVE SPECIES?

 

The easiest way to send us information about the species you have seen is via our online form. Please select one of the three options below to send us your record(s):


 


 

(e.g. more than 20 records; including records of more than one species,
at more than one location and on several different dates 
- please send as excel spreadsheet where possible using our template)

DOWNLOAD THE NBIS RECORDING SPREADSHEET HERE AND THEN CLICK ABOVE TO EMAIL US YOUR RECORDS
 (or email nbis@norfolk.gov.uk)
 



 

....SOME BASIC INFORMATION:

 

New Zealand Pigmyweed/Australian Swamp-stonecrop (Crassula helmsii)

Description: Aquatic perennial with small yellow-green, succulent leaves and solitary white flowers.
Where to look: Still or slow flowing freshwater. The plant also has a terrestrial phenotype that can be found around ponds and lake margins.
Why is it a problem? Forms very dense mats that can choke waterways, impede drainage and cause flooding.

 

 

Floating pennywort (Hydrocotyle ranunculoides)

Description: This aquatic plant has characteristic, kidneyshaped leaves which can be freefloating or emergent. It has fleshy stems and fine, white roots.
Where to look: Emergent or floating on the surface of still or slowly moving freshwater.
Why is it a problem? With a peak growth rate of 20cm per day, floating pennywort can rapidly dominate a water body!

 

 

Himalayan balsam (Impatiens glandulifera)

Description: An annual herb with bright pink-purple, trumpet-shaped flowers, fleshy stem and explosive seed heads.
Where to look: Prefers to grow in damp areas, and is particularly abundant on river banks where it out-competes native vegetation
Why is it a problem? Die back in winter leaves river banks bare and susceptible to erosion.

 

Giant hogweed (Heracleum mantegazzianum)

Description: Large plant with umbrellashaped flowers and sharply divided leaves, growing up to 5m tall. The stems are usually covered with sharp bristles, and have distinctive purple patches. Each flower can release up to 50,000 seeds!
Where to look: Found in a variety of habitats, but common on riverbanks and roadside verges.
Why is it a problem? The poisonous sap of this plant can blister skin.

 

Japanese knotweed (Fallopia japonica)

Description: Tall herbaceous perennial with bamboo like stems covered with purple speckles. The shield-shaped leaves are 10-15cm long with a flat base. White flowers in late summer.
Where to look: Widespread throughout the UK. Often found in or adjacent to, brown-field sites and along river banks.
Why is it a problem? The root system and strong growth of this plant can damage foundations. Dense colonies crowd out other herbaceous species.

 

Tree of heaven (Ailanthus altissima)

Description: A tree with large pinnate leaves each consisting of around 11-25 pairs of leaflets reaching 7-12cm in length. Flowers are a yellowish green to red in colour. When broken, twigs have a distinctive unpleasant odour.
Where to look: Urban areas such as railway banks, waste ground and parks.
Why is it a problem? Extensive growth can damage sewers, pavements and building foundations. Sap is mildly toxic and can cause inflammation of the
skin.

 

We have created a dedicated FAQs page and advisory service to support the Urban Invaders campaign.
Find out more: www.rinse-europe.eu