Species

Information

On this page you will find information, advice and useful links for: Japanese Knotweed Himalayan Balsam, Giant Hogweed and some of the other non-native invasive weeds.

Japanese Knotweed

Japanese knotweed (Fallopia japonica) Giant knotweed (Fallopia sachalinensis) Hybrid knotweed (Fallopia x bohemica)

Facts:

Habitat: Grows in most environments in bamboo like clumps. Flowers: Aug – Oct. Creamy white, elongated clusters. Leaves: Green heart-shaped up to 12 cm long. Stems: Up to 3m tall. Green with red speckles and joints. Hollow and bamboo like.

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The Non Native Species Secretariat has produced a very detailed ID sheet for this species.  See Non-native Species Secretariat ID sheets

How to control it:

Japanese Knotweed can spread extremely easily and quickly and can be very difficult and costly to control or eradicate. A piece of the plant no bigger than the size of your fingernail can grow in to a new plant and parts of the plant can survive the composting process. The plant is often spread by humans. It is therefore very important that Japanese Knotweed is controlled and disposed of correctly to prevent its spread.

The documents below gives detailed information on the best ways to control and dispose of Japanese Knotweed.

Link: Environment Agency – Japanese Knotweed Code of Practice – Managing Japanese Knotweed on Development sites:

For more guidance please also see the useful information and links page below.

Click on the pictures above to enlarge them.

Himalayan Balsam (Impatiens glandulifera)

Facts:

Habitat: Grows predominantly in damp areas such as on watercourse banks in dense clumps. Flowers: Jun – Sept. Purplish pink to very pale pink. Slipper shaped on long stalks. Leaves: Green, spearhead shaped with serrated edges, up to 15cm long Stems: Pinky-red colour up to 2.5 m tall, hollow, brittle and sappy

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The Non Native Species Secretariat has produced a very detailed ID sheet for this species.  See Non-native Species Secretariat ID sheets

How to control it:

Himalayan Balsam spreads very easily and rapidly. Each plant produces many seeds in pods that explode and can shoot seeds many meters. It is easier to control than many other invasive species by pulling up by the roots, but this must be completed before the seed pods have had time to develop. The document below give further information on the best ways to control and dispose of Himalayan Balsam.

For more guidance please also see the useful information and links page below.

Click on the pictures above to enlarge them.

Giant Hogweed (Heracleum mantegazzianum)

Facts:

Habitat: Grows in many environments such as on the banks of watercourses

Flowers: Jun – July. Small white flowers clumped in a large (up to 50 cm) umbrella bouquet.

Leaves: Green up to 1.5 m long with a jagged appearance.

Stems: Up to 5m tall. Green with red blotches. Hollow and up to 10 cm across.

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The Non Native Species Secretariat has produced a very detailed ID sheet for this species.  See Non-native Species Secretariat ID sheets

Not to be confused with smaller similar species such as Hemlock……. ITS THE BIG ONE!

BEWARE – DO NOT TOUCH GIANT HOGWEED!

Contact with this plant can result in blistering to the skin. – The plant is covered in fine hairs containing sap that makes skin sensitive to sun light. – Seek immediate medical advice if blistering occurs after contact.

Hogburns

How to control it:

Giant Hogweed produces thousands of seeds per plant. These seeds can survive and lay dormant in the soil for many years before emerging and developing into a new plant. It is therefore important that the plant is controlled in a manner that means that the seeds can not escape from the plant.

PLEASE BE AWARE OF THE HEALTH ISSUES INVOLVED IN DEALING WITH THIS PLANT (see above). The document below gives further information on the best ways to control and dispose of Giant Hogweed.

For more guidance please also see the useful information and links page below.

Click on the pictures above to enlarge them.

Other problem weeds

Floating Pennywort (Hydrocotyle ranunculoides)

Found forming mats on the water surface in wet ditches and ponds. Circular or kidney shaped leaves up to 18 cm across. No flower.

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The Non Native Species Secretariat has produced a very detailed ID sheet for this species.  See Non-native Species Secretariat ID sheets

Australian swamp stonecrop (Crassula helmsii)

Found forming mats on the water surface in ponds and lakes. Small white flowers Jun – Sept. Yellowish green fleshy looking leaves.

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The Non Native Species Secretariat has produced a very detailed ID sheet for this species.  See Non-native Species Secretariat ID sheets

Parrots Feather (Myriophyllum aquaticum)

Found forming mats on the water surface in ponds and lakes. Feathery looking bright green leaves. No flowers.

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The Non Native Species Secretariat has produced a very detailed ID sheet for this species.  See Non-native Species Secretariat ID sheets

For further information on Identification of non-native invasive species please see the links to useful documents below.

Link: Avon Invasive Weed Forum identification guide – pdf document

Link: Non-native species secretariat Id sheets

 

 

For further information on the Control of non-native invasive species please see the links to useful documents below:

Link: Managing Japanese Knotweed: Code of Practice

 

Link: Environment Agency Guidance for the control of invasive weeds in or near fresh water

Link: Royal Horticultural Society information

 

For more information on pond species and how to stop the spread of non-native invasive species see link below to the Be Plant Wise Campaign website.

Link: Be Plant Wise

 

 

 

 

 

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