Japanese Knotweed ID – Autumn

Knotweed ID AutumnKey features:

  • Mature clumps 2-3 metres high, with dense stands of yellowing bamboo-like stems up to 20-25mm diameter which gradually turn brown and dry as colder weather sets in.
  • Distinctive masses of bare flowering spikes in clusters from nodes towards the ends of branching zig-zag stems.
  • Where leaves are still present, a single shield-shaped leaf 10-12cm long with a flat base from each node.

Similar non-invasive species:

  • Hazel – looks very similar in autumn at first glance but leaves are much more heavily veined and ribbed, stems are straight rather than zig-zag, and have no flower spike remnants at ends.

More information:


WACA 1981 Schedule 9 Plant List Update

The two terrestrial plants that have been on Part II of Schedule 9 of the Wildlife & Countryside Act since it’s introduction in 1981 – Japanese Knotweed and Giant Hogweed – are now quite well known, recognized and properly controlled on construction sites. However, on 6th April 2010, a major update of Schedule 9 came into effect, adding a great many new plants to Schedule 9, many of which are relatively well known as common garden or ornamental pond plants.

My consolidated list of Schedule 9 plants (England &  Wales) with the four original (1981) plants highlighted in bold now looks like:

Terrestrial Plants:

  • Allium paradoxum (Few-flowered Leek), A. triquetrum (Three-cornered Garlic)
  • Carpobrotus edulis (Hottentot Fig)
  • Cotoneaster bullatus (Hollyberry Cotoneaster), C. horizontalis (Cotoneaster), C. integrifolius (Entire-leaved Cotoneaster), C. microphyllus (Small-leaved Cotoneaster), C. simonsii (Himalayan Cotoneaster)
  • Crocosmia x crocosmiiflora (Montbretia)
  • Disphyma crassifolium (Purple Dewplant)
  • Fallopia japonica (Japanese Knotweed), F. japonica x F. sachalinensis (Hybrid Knotweed), F. sachalinensis (Giant Knotweed)
  • Gunnera tinctoria (Giant Rhubarb)
  • Heracleum mantegazzianum (Giant Hogweed)
  • Impatiens glandulifolius (Himalayan Balsam)
  • Lamiastrum galeobdolon subs argentatum (Variagated Yellow Archangel)
  • Parthenocissus inserta (False Virginia Creeper), P. quinquefolia (Virginia  Creeper)
  • Rhododendron luteum (Yellow Azalea), R. ponticum (Rhododendron), R. ponticum x R. maximum (Rhododendron)
  • Rosa rugosa (Japanese Rose)

Aquatic Plants

  • Azolla filiculooides (Water Fern)
  • Cabomba caroliniana (Fanwort, aka Carolina Water-Shield)
  • Crassula helmsii (Australian Swamp Stonecrop, aka New Zealand Pygmyweed)
  • Eichhornia crassipes (Water Hyacinth)
  • Elodea spp (All Waterweeds)
  • Grateloupia luxurians (Red Algae)
  • Hydrocotyle ranunculoides (Floating Pennywort)
  • Lagarosiphon major (Curly Waterweed)
  • Ludwigia grandiflora (Water Primrose), L. peploides (Floating Water Primrose), L. uruguayensis (Water Primrose)
  • Myriophyllum aquaticum (Parrot’s Feather)
  • Pistia stratoites (Water Lettuce)
  • Sagittaria latifolia (Duck Potato)
  • Salvinia molesta (Giant Salvinia)

Marine Plants

  • Codium fragile (Green Seafingers)
  • Macrocystis pyrifera (Giant Kelp)
  • Sargassum muticum (Japanese Seaweed)

As has been the case with Japanese Knotweed and Giant Hogweed for the past 30 years, it is now a Section 14 offence to cause any of these plants to grow in the wild, and this includes inadvertently spreading plant material during construction operations. Any soil or plant waste containing viable growing material from any of the above plants is classed as “controlled waste” under the Waste Duty of Care, and must be dealt with as such.

I now cover invasive plants as part of my Wildlife & Biodiversity Masterclass. Please contact me if you would like more details of this course.

Japanese Knotweed

Japanese Knotweed (Fallopia japonica) is a fast growing perennial plant that has no native predators in the UK, and can regenerate from tiny fragments of material (0.7 grammes in the case of roots). Since its introduction as a “must have” plant on Victorian estates in the mid-nineteenth century (it thrived anywhere, including poor ground), it has become a serious nuisance in the wild, displacing native plants and their associated wildlife. Due to its deep-rooted nature (up to 7m horizontally from the crowns and 4m deep) its is very difficult to completely excavate or kill with herbicide, and unless comprehensively treated, will soon recover and resume being a problem.

Its frequent presence on development sites, resistance to quick eradication, wide root spread, and ability to regenerate from tiny fragments makes it a unique challenge that if not dealt with properly, opens both contractors and developers to the risk of prosecution. If you have time (at least a year) its always better to eradicate Knotweed on site before you start work.

The Legal Position

Japanese Knotweed is one of over 40 plants listed in Schedule 9 Part II of the Wildlife & Countryside Act 1989, which makes it a Section 14(2)(a) offence to “plant or otherwise cause (Japanese Knotweed) to grow in the wild”. The penalties for a Section 14 offence were modified by the Countryside & Rights of Way Act 2000, and a magistrates’ court can now impose a fine of up to £5000 on conviction, a six month prison sentence, or both.

The legislation applies to both deliberate and accidental spreading, and sites contaminated with Japanese Knotweed need to be carefully controlled to avoid breaches and potential Regulatory action. (This includes disposal of Knotweed waste at a site not licensed to receive it.) However, it should be noted that the legislation applies to “spreading” – it is not currently illegal to have Japanese Knotweed growing on your land providing you don’t spread it into the wild and it doesn’t cause a nuisance to neighbours (although the latter is a civil liability rather than criminal offence).

Dealing with Japanese Knotweed

The Environment Agency has produced a Knotweed Code of Practice which sets out the actions expected of Developers and Contractors when dealing with Japanese Knotweed on site.

Disposing of Japanese Knotweed, and soil contaminated with Japanese Knotweed roots

Due to its ability to regenerate from tiny fragments of viable material after a dormancy of up to 20 years, soil and waste containing Japanese Knotweed is considered to have the potential to cause “ecological harm”, and as such is considered to be a Controlled or Directive waste under the Waste Management Licensing Regulations 1984. As such, the producers of Knotweed waste have obligations for its proper treatment under the Waste Duty of Care, including ensuring that it is only disposed of at a site which has an appropriate permit to receive it. (Note – as the material has to be buried at a depth of 5m or more, not all “non-hazardous” sites are able to receive it – permits should be carefully checked.)

With regard to the description of the waste on the Waste Transfer Note (WTN), the Environment Agency have previously advised that the materials for disposal should be segregated on site and the following LOW Regs 2005 codes used with the bold additions to the descriptions clearly stated on the WTN:

  • Japanese Knotweed vegetation – 20 02 01 “Biodegradable waste containing Japanese Knotweed
  • Soils contaminated with Japanese Knotweed roots – 17 05 04 “Soils and stones other than those mentioned in 17 05 03* containing Japanese Knotweed

Do you suspect you have Japanese Knotweed on your site? – Give me a call! Looking for a training course on Invasive Plants? – Check out my Wildlife & Biodiversity Masterclass