INVASIVE SPECIES
Clean Estates recognise the importance of identifying certain weed varieties as an invasive species.
Japanese Knotweed, Giant Hogweed and Himalayan Balsam all fall into this classification and are a common cause of concern for many Property Managers.
These plants can cause structural damage resulting in Health and Safety issues.
We are pleased to advise you that Clean Estates Landscaping Teams are fully trained to identify and report upon invasive weed species on sites, as part of our Estates Landscaping and Cleaning range of services.
Following identification of the weed species, Clean Estates can provide a comprehensive treatment programme, using experienced staff who are all well versed in this process, in line with our company Health & Safety procedures.
All staff are trained to NPTC standards, are competent in the safe use of pesticides and all have attained their PA1 & PA6 certification.
Treatments can be tailored for a 1, 2, or 3 year basis, which may be necessary particularly, when treating Japanese Knotweed.
We only use approved waste contractors for removal of any waste from site.
Here are a few details about a few invasive species :
Himalayan Balsam
Himalayan or Indian balsam (Impatiens glandulifera) was introduced to Britain in 1839, but escaped from gardens and rapidly colonised riverbanks and areas of damp ground. Himalayan balsam grows in dense stands that suppress the growth of native grasses and other flora. In the autumn, the plants die back, leaving the banks bare of vegetation and vulnerable to erosion.
Facts and figures
Native range: Western Himalayas
Stem:
Pinky-red colour
Up to 3m tall - tallest annual plant in Britain
Hollow and jointed
Sappy and brittle
Leaves:
Spear-shaped, with serrated edges
Shiny and dark green with a dark red midrib
Up to 150mm long
Opposite or in whorls of three
Flowers:
Purplish-pink to pale pink
Slipper-shaped, on long stalks
June – October
Seeds:
White, brown or black
Produced from July – October
4-7mm diameter
4 – 16 seeds per pod
Control: Control measures should aim to prevent flowering and if this is achieved before seeds are set, eradication is possible in two to three years.
Chemical control: can use glyphosate or 2,4-D amine. Need to be used whilst plant is actively growing in early spring for best effect.
Cutting/mowing/strimming: cut at ground level using a scythe, before the flowering stage in June. Do not cut earlier as this promotes greater seed production in any plants that regrow. Cutting should be repeated annually until no more growth occurs.
Pulling: shallow-rooted plants can be pulled up very easily and disposed of by burning or composting, unless seeds are present.
Grazing: Grazing by cattle and sheep is effective from April throughout the growing season. It should be continued until no new growth occurs.
Picture: Himalayan Balsam
Giant Hogweed
Giant hogweed (Heracleum mantegazzianum) was introduced to Britain in 1893 as an ornamental plant. It escaped from gardens and now colonises many areas of wasteland and riverbanks. It forms dense colonies that suppress the growth of native plants and grasses, leaving the banks bare of vegetation in winter and increasing the risk of erosion and recolonisation from seeds washed downstream.
Legislation: The Wildlife and Countryside Act 1981 provides the primary controls on the release of non-native species into the wild in Great Britain. It is an offence under section 14(2) of the Act to ‘plant or otherwise cause to grow in the wild’ any plant listed in Schedule 9, Part II. This includes Giant hogweed.
HEALTH HAZARD
The stems, edges and undersides of the leaves bear small hairs containing poisonous sap, and the slightest touch causes painful blistering and severe skin irritation. Unshaded habitats with high soil nitrate levels tend to produce greater quantities of toxins in the plant. Contact with cut material in sunlight produces a skin reaction in almost all cases. Blistering symptoms occur 24- 48 hours after exposure, and dense pigmentation is visible after 3 – 5 days. This may persist for 6 years or more. Protective clothing must be worn.
Facts and figures
Native range: Caucasus mountains.
Lifecycle: It is a perennial plant that takes up to 4 years to mature and flower, after which it dies.
Stem: Green with dark-red or purple blotches. Hollow Up to 100mm across Up to 5m tall.
Leaves: Dark green, in a rosette Jagged appearance and spiky at the ends Lower leaves up to 1.5m long.
Flowers: White Several hundred in large umbrella-like flower heads up to 500mm Across. June – July.
New plants: Each flowerhead produces up to 50,000 seeds (approx. 10mm x 7mm) that are easily dispersed by water, so the plant disperses rapidly along watercourses. Seeds may remain viable for up to 15 years.
Control: Aim – to kill the plant or prevent flowering.
Chemical control is most effective. Spraying can start as soon as the plant is about 1m high, usually in March and continue throughout the summer. More than one application is often necessary and follow-up spraying will be required to kill seedlings in subsequent years.
Non-chemical control Cutting down stems with a sharp scythe before flowering will help control this plant. Flail mowing is possible but with extreme caution due to the risk of being sprayed with sap. Protective clothing should be worn.
The crown may be dug out just below ground to prevent regrowth this provides good control.
Grazing by cows and sheep will suppress growth but will not eradicate it. It is essential to establish vegetation quickly after control measures have been applied, as dense grass sward tends to discourage seed germination.
Disposal: Should be taken to a landfill site or by piling on site and composting.
Picture: Giant Hogweed
Japanese Knotweed
Japanese knotweed was brought to Britain as an ornamental garden plant in the mid-nineteenth century. However since then it has become widespread in the wild and causes serious problems by displacing native flora and causing structural damage.
Legislation: The Wildlife and Countryside Act 1981 provides the primary controls on the release of non-native species into the wild in Great Britain. It is an offence under section 14(2) of the Act to ‘plant or otherwise cause to grow in the wild’ any plant listed in Schedule 9, Part II. This includes Japanese Knotweed.
There are 3 species of invasive knotweed in the UK. Japanese knotweed (Fallopia japonica) – the most widespread and troublesome bankside species. Giant knotweed (Fallopia sachalinensis) Hybrid knotweed (Fallopia x bohemica) – a cross between Japanese and giant knotweed.
Facts and figures
Native range: Eastern Asia
Stem: Up to 2-3m tall.
Green, with red or purple specks.
Forms dense cane-like clumps.
Leaves: Green, shield or heart-shaped, with a flat base.
Up to 120mm long.
Flowers: Creamy clusters borne on the tips of most stems.
August – October
Roots: Consist of rhizomes, which are yellow, when cut.
The rhizome system can reach 7m from the parent plant and can be up to 3m deep.
New plants: New plants can grow from a piece of rhizome the size of a little finger nail and the crown, located at the base of the stem will also produce new plants.
Control: Near water chemical control can be achieved with herbicides containing glyphosate. Spraying both the top and underside of leaves improves control.
Cutting: should be done extremely carefully using a hand sythe to avoid spreading stem fragments. Flail mowing must not be carried out. Continue cutting every 2-4 weeks to reduce both above and below ground biomass.
Pulling: Uproot stems by pulling from the base – best done from June onwards.
Grazing: Grazing of shoots by horses, sheep and goats keeps the plants in check, provided previous dead growth is removed.
Digging: Digging out rhizomes and disposing of the spoil is an expensive option and often impracticable. The spoil can be removed from a site as special waste, disposed on-site at least 10m deep, or the material can be sieved through a 20mm mesh and the spoil reused on site.
Spring Cut new growth. Dig out rhizomes or spray new growth with Glyphosate. Excavate soil and dispose of on site or take to landfill as special waste, under license. Summer Cut new growth. Dig out rhizomes or spray with glyphosate. Autumn Cut new growth. Dig out rhizomes and spray with glyphosate. This is the most effective time for glyphosate application.
Disposal: The stems die back in winter but take up to 3 years to decompose. Japanese knotwood crowns should neither be composted nor removed from a site without a waste license. Burn cut stems on site or bury 10m deep.
Picture: Japanese Knotweed
