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Knotweed Growth (time-lapse)

This video shows how destructive knotweed can be when left untreated.​

  • Knotweed roots will spread up-to 7m from the visible plant

  • New shoots can easily penetrate concrete and tarmac surfaces

  • Building structures, walls and foundations can be severely damaged

There are four non-native, invasive, regulated knotweed species contained within the European Communities (Birds and Natural Habitats) Regulations 2011:

  1. Bohemian knotweed (Fallopia x bohemica) - Hybrid of Fallopia sachalinensis and Fallopia japonica

  2. Giant knotweed (Fallopia sachalinensis)

  3. Himalayan knotweed (Persicaria wallichii) 

  4. Japanese knotweed (Fallopia japonica)

 

All four knotweed species are herbaceous perennial plants that are similar in appearance.

 

Knotweed have green hollow bamboo-like stems that are mottled red. Plants have small white grouped flowers.

 

The Fallopia species have alternate leaves arranged in a zig-zag pattern along the stems. Persicaria leaves are elongated and lance-like.

 

Rhizomes are brown outside, snap easily and are orange coloured on the inside.

 

Species can normally be identified by leaf shape and size.

Knotweed Leaf Identification Guide (5 Species)

Non-native, invasive knotweeds are plants that can grow vigorously and are easily spread from small fragments of the plant. knotweed have a negative impact on area such as:

 

  • Road visibility

  • Biodiversity

  • Drainage

  • Water quality

  • Infrastructure

  • Housing development

 

The European Communities (Birds and Natural Habitats) Regulations 2011 contain important provisions addressing invasive species.

 

The threat of Invasive knotweeds outline obligations for local authorities, public bodies, contractors on how invasive knotweed species are managed.

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Regulations outline the obligations for local authorities:

Public authorities must ensure that they are compliant with the Regulations. Activities which public authorities or their contractors undertake which may be relevant to Regulations 49 and 50 include:

  • Hedge cutting

  • Soil movement

  • Infrastructure development

  • Landscaping

  • Procurement

  • Planning (development control & forward planning)

 

Local authorities have the ability to initiate summary proceedings for offences.

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If charged with any offence under these Regulations defence must prove ‘all reasonable steps and exercised due diligence to avoid committing the offence’. 

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knotweed, and the EC Regulation key points:

 

Regulation 49: Prohibition on introduction and dispersal of certain species.

This places restrictions on the introduction of any plant species listed in Part 1 of the Third Schedule. A person shall be guilty of an offence if they:

plant , disperse , allow or cause to disperse , spread or cause to grow

the plant in the Republic of Ireland.

 

Regulation 49 addresses both plants and animals but only plants are addressed on this page.

 

Regulation 50: Prohibition on dealing in and keeping certain species

Section 50 of the Regulations make it an offence to or intend to:

import, buy, sell, breed, reproduce or propagate, advertise, offer or expose for sale, publish a price list, transport or distribute; any animal or plant species or vector material listed in the Third Schedule.

 

Third Schedule, Part 3: Vector materials. Two vector materials are referred to. One is blue mussel seed and the second is:

Soil or spoil taken from places infested with Japanese knotweed, Giant knotweed, or their hybrid Bohemian knotweed.

 

Regulation 50 comes into effect on the date the Minister gives public notice.

 

Activities can be undertaken in accordance with a granted licence.

 

35 plants are listed in the Third Schedule Parts 1 & 2.

Download the Regulations: www.irishstatutebook.ie/pdf/2011/ en.si.2011.0477.pdf

Managing knotweed infested land in a timely and appropriate way can avoid:

  • Excessive remediation costs

  • Prosecution

  • Claims for compensation

  • Damage to buildings

  • Damage to hard surfaces 

  • Environmental damage.   

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Management objectives:

  • Prevent further introduction or spread by undertaking biosecurity measures

  • Detection and mapping of knotweed informs threat level and management approach

  • Eradicate stands of knotweed early in its invasion especially in priority high risk areas of spread and impact. The earlier the better for capacity and cost to eradicate

  • Control areas of infestation from spread and further expansion

 

It is also always best practice to seek professional advise when managing any invasive non - native species. Badly planned or improper management can lead to further con and prosecutions.

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