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CLIENT FOCUSED SOLUTIONS FOR
INVASIVE LANDSCAPES
Giant Hogweed
Himalayan Balsam
Horsetail
Other terrestrial invasives
Other aquatic invasives
Knowledge base

Other Invasive Vegetation

Currently containing 54 vegetative species. The Wildlife and Countryside Act imposes strict restrictions on many of the plants found within brownfield, greenfield and aquatic sites. Our consultants have a broad knowledge of these plants and are able to develop cost effective, pragmatic management solutions, whatever may be found.

 

Giant Hogweed

Introduced to the UK as a garden ornamental in the 1800’s from South West Asia and a member of the carrot family (Apiaceae). Giant Hogweed produces plants lasting several years and is much larger than our native hogweed / cow parsnip (Heracluem sphondylium). In the summer large white umbrella-like flowers emerge producing thousands of seeds that easily spread, either persisting in the soil for several years or forming new infestations the following year.

Giant Hogweed is now widespread across the UK invading habitats such as riverbanks, roadsides and waste ground. The sap of this highly invasive weed can cause severe and painful skin blisters on humans as well as being toxic to grazing animals. The invasive, persistent and harmful nature of this weed has led to it being included in legislation such as Schedule 9 of the Wildlife & Countryside Act 1981 and classified as a controlled waste (Environmental Protection Act 1990). 

Successful management within a site requires controlling the weed, seed and movement of soil. Contaminated soils can be removed offsite by a licenced waste carrier ensuring the removal of all life stages. Alternatively, the weed can be managed using herbicides during the spring and early summer (i.e. before flowering) over several seasons until the seed-bank has been depleted.  What is difficult is controlling re-establishment if a neighbouring infestation is unmanaged, care should be taken to identify possible sources.

 

Himalayan Balsam

Introduced from the Himalayas as a garden ornamental in the mid 1800’s it is related to the garden plant Busy lizzie and commonly known as policeman’s helmet. In the mid-summer it produces attractive pink flowers which develop into seed pods that explode shedding thousands of seeds in the late summer. The seeds survive the winter in the soil and germinate the following spring forming dense carpets of seedlings that mature into adult plants.

Balsam is now widespread across the UK forming large dense stands that exclude native species in lowland wetlands, riverbanks, and damp woodlands. When it dies back in the winter it can leave riverbanks exposed to erosion during heavy rainfall, which can impact on watercourses and increase flood risk. The seed can also survive transportation via watercourses making it a highly invasive weed.

Successful management within a site requires controlling the weed, seed and movement of soil. Contaminated soils can be removed offsite by a licenced waste carrier ensuring the removal of all life stages. Alternatively, the weed can be managed using herbicides during the spring and early summer (i.e. before flowering) over several seasons until the seed-bank has been depleted.  What is difficult is controlling re-establishment if there are sources of seed further upstream which where a whole catchment level management plan is advantageous.

 

Horsetail

Field horsetail (Equisetum arvense) is often confused with Mare's tail (Hippuris vulgaris). Although superficially looking similar, they are very different with the former having a wide range of habitats and the latter preferring aquatic habitats. The stems are slender with the leaves being very fine protruding as whorls of long rough hair like structures forming a horsetail like structure. These plants have deep roots (rhizome) and spread via microscopic spores.

Field horsetail is native to the UK and is not an invasive non-native species. However, it can be considered a nuisance weed as a result of it growing through gaps in paving, cracks in driveways and general persistence in landscaped areas. In countries such as New Zealand where it has been introduced it is an invasive non-native species and can impact on agriculture and natural ecosystems.

The plant is difficult to control using herbicides due to the fine leaves which result in reduced absorption of the active ingredients and although the top of the plant may initially be controlled, it will eventually re-emerge from the deep rhizome. Mechanical removal can remove the weed, but the rhizome can go down several metres into the soil and if locally abundant can require large volumes to be removed. It should be remembered that this plant is native, abundant and spreads via spores making long term management necessary to minimise impact.

 

Other terrestrial invasives

There are 27 species of terrestrial plant listed within the WCA for England & Wales, other than Japanese knotweed, Himalayan balsam and Giant hogweed. Other species include many common garden and landscaping plants e.g. Montbretia, Virginia creeper, Cotoneaster, Rhododendron, and Japanese rose.

 

Other aquatic invasives

There are 14 freshwater aquatic plants and 13 marine within the WCA for England & Wales. Many of the freshwater weeds have different growth habits: some growing entirely under the water (submerged) e.g. curly waterweed; others grow under the water but emerge at the surface (emergent) e.g. parrot’s feather; and some can be free floating e.g. water fern. There are also some species that are amphibious / marginal, and others that grow in all these situations e.g. New Zealand Pygmy Weed (Crassula helmsii). All these plants are highly invasive and can spread via fragments. Coupled with their growth habits these plants can be difficult to control, therefore management should focus on long-term control and biosecurity with complete eradication often being difficult.

 

Knowledge base

Ebsford Environmental have a wealth of experience in managing invasive non-native species from a wide range of situations: from residential to development sites, and on a landscape level e.g. water industry. Our specialists have varying backgrounds including construction and land remediation, water, ecology, agriculture.

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