Frequently Asked Questions

HOW CAN YOU KILL JAPANESE KNOTWEED?2018-10-01T17:17:40+00:00

Japanese knotweed infestations can be controlled and eliminated through a variety of methods. Depending on factors such as timescale, location of infestation and its surrounding environment the method can vary but through correct application and management Japanese knotweed growth can be stopped and prevented from returning. The main methods of control are:

Chemical – Qualified and competent personnel are permitted to use herbicides to control and eliminate Japanese knotweed. The application method and specific chemical used will depend on factors such as the infestations proximity to watercourses and local wildlife.

Burial – If time is a factor and it is unfeasible to wait for the numerous growing seasons that herbicide treatment may take to eradicate an infestation Japanese knotweed can be excavated and buried on site. All material contaminated with Japanese knotweed is encased in a root barrier membrane that prevents further growth and buried at a depth greater than 5m below the surface to prevent the material being disturbed and re-infesting the area.

Bund – If burial on site is not an option a bund can be created by designating an area of the site to place all material and soil contaminated with Japanese knotweed. The bund is then treated with herbicide allowing the original area of infestation to be developed or managed without the presence of Japanese knotweed being an issue. This method can be applied if there is sufficient time and space to relocate contaminated material and treat it on site, preventing the high costs of disposing Japanese knotweed at a licensed waste management facility off site.

Cutting – Japanese knotweed stems can be cut and dried out however this will only address the growth above ground and will take many years to effectively control the infestation without the use of chemicals or digging out the Japanese knotweed rhizome.

Burning – As with cutting this method can be ineffective without excavating Japanese knotweed rhizome from the soil and burning it with all plant material.

Biological Control – After careful research and development, tiny plant-eating insects called psyllids have been identified as a possible means to control Japanese knotweed, with tests being done to establish whether to release them nationwide. The ‘knotweed bugs’ have been released in some parts of England as part of a trial. Although they may control the Japanese knotweed they will not eradicate it fully otherwise the bugs would have nothing left to eat and they would die.


Giant hogweed can cause serious skin irritation and burns often becoming apparent 15-20 hours after direct contact with the plants phototoxic sap. Burns to the skin sustained from exposure to the sap can result in scarring and recurring skin sensitivity to ultraviolet light. Contact directly to the eyes can cause temporary blindness, in some cases resulting in permanent damage. Giant hogweed can be found growing near rivers and streams where seeds can be easily dispersed causing erosion to river banks as they develop and die back in the winter. The production of so many seeds annually can help Giant hogweed to rapidly colonise areas, denying native species the chance to grow unhindered and reducing biodiversity in the local environment. This can have devastating effects to the surrounding wildlife, tampering with the delicate balance of the ecosystem and potentially causing irreversible damage.


Japanese knotweed is able to colonise a variety of urban and rural environments. Due to its ability to exploit weaknesses in construction material, such as concrete and tarmac, new knotweed growth can cause damage to structures and roads thus affecting the value of property as it rapidly develops. As Japanese knotweed grows along riverbanks it is able to colonise large areas as stems and rhizomes are carried downstream to ultimately spread the infestation causing severe damage to flood defence structures. Ecosystems can be disrupted by the presence of Japanese knotweed which can starve the surrounding native plants of resources, seriously impacting on the delicate balance of local food chains.

WHAT DOES GIANT HOGWEED LOOK LIKE?2018-10-01T17:18:38+00:00

New Giant hogweed growth appears as dark green spiked leaves in March/April developing large hollow ribbed stems green in colour with spots of purple. Tiny, coarse hairs cover the stem and base of the leaves. Mature Giant hogweed produces large white flower heads which can contain up to 50,000 broad, flattened seeds. Once fully developed, Giant hogweed can stand 5m tall with enormous jagged leaves spanning 1m, shielding the surrounding vegetation from sunlight and preventing their growth.


The most striking characteristics of Himalayan balsam are the pink/purple hooded petals and the strong balsam scent, attracting numerous insects such as bees and butterflies. The hollow stem of the plant appears reddish-translucent and reaches heights of 2-3m when fully developed. The serrated, pointed leaves of Himalayan balsam are green in colour and grow 5-18cm long, growing from nodes in the stem in pairs or groups of three. Adult plants produce a number of delicate diamond shaped seed pods that disperse their contents by “exploding” on physical contact, curling back each of the five sections of the pod projecting seeds up to 7 metres.


Japanese knotweed emerges as small asparagus-like shoots green/purple in colour. As the plant develops it produces small red/green shield-shaped leaves growing from the stem’s many distinct raised nodes or ‘knots’. Once mature, the leaves become a vibrant green colour reaching lengths of up to 120mm.  The red/green stems of adult Japanese knotweed have a hardy bamboo- like appearance which grows in thick clumps or ‘stands’. During the months of September and October, creamy white flowers are produced, growing in clusters at the end of the stems. As the plant sheds its leaves and dies off, the stems become hollow brown skeletal remains that are easily broken. The dead stems often remain upright amongst new growth during the following season.

WHAT IS GIANT HOGWEED?2018-10-01T17:18:13+00:00

Giant hogweed (Heracleum mantegazzianum) commonly known as cartwheel-flower, wild parsnip, wild rhubarb, or giant cow parsnip is a non-native invasive perennial plant often found growing near watercourses, motorways and waste ground across the UK. Native to the Caucasus Region and Central Asia, Giant hogweed was introduced to Britain as an ornamental plant during the 19th century and has since thrived due to its natural resistance to frost and huge number of seeds produced.

WHAT IS HIMALAYAN BALSAM?2018-10-01T17:21:04+00:00

Himalayan balsam (Impatiens glandulifera) is an annual plant native to the Himalayas. Also know as Policeman’s HelmetBobby Tops and Gnome’s Hat Stand due to the unusual shape of its petals, Himalayan balsam can be found throughout the UK where it is classed as an invasive species. Originally introduced to the UK by Victorian horticulturists in the 1830s, Himalayan balsam quickly spread throughout the nation’s network of watercourses and can be found growing on riverbanks and rural areas to this day.

WHAT IS JAPANESE KNOTWEED?2018-10-01T17:15:43+00:00

Japanese knotweed (Fallopia japonicais a large perennial plant that grows throughout much of the UK. It was imported to Britain from Japan during the mid 19thcentury as popular ornamental feature to many gardens. Today, Japanese knotweed is recognised as one of the most invasive species present in the UK and is known for rapidly spreading and causing substantial damage to areas where it is present.

WHY IS GIANT HOGWEED A PROBLEM?2018-10-01T17:20:00+00:00

Giant hogweed is a phototoxic plant, secreting a toxic sap from the stem and leaves posing a serious health risk to humans and animals. If the sap comes into contact with bare skin and is then exposed to a source of ultraviolet radiation such as sunlight, it can cause severe burns and blistering. Due to the unusual appearance of the plant it can often be disturbed by passersby, particularly children, who are most at risk from exposure to the sap. As a result, the presence of Giant hogweed on or around footpaths and roads can restrict public access. Growth can affect the surrounding environment as it rapidly colonises large areas with dense clusters, their enormous leaves starving local plant life of sunlight.

WHY IS HIMALAYAN BALSAM A PROBLEM?2018-10-01T17:22:00+00:00

An adult Himalayan balsam plant can produce up to 800 seeds enabling a small colony to rapidly spread, especially along riverbanks where it is commonly found. Buoyant seeds can be carried downstream to colonise far from the parent plant and are even capable of germinating underwater. Growing in dense clusters Himalayan balsam is able to prevent local native plant species from developing by starving them of sunlight and minerals.

WHY IS JAPANESE KNOTWEED A PROBLEM?2018-10-01T17:16:41+00:00

Being a non – native species to the United Kingdom, Japanese knotweed is able to grow rapidly and in many cases dominate its surrounding environment. Unaffected by the natural controls such as predators and diseases that target the native flora, Japanese knotweed infestations can quickly spread. Japanese knotweed is classed as an invasive weed in the UK and is included in the Wildlife and Countryside Act 1981, making it an offence to ‘plant or otherwise cause Japanese knotweed to grow in the wild’. Significant costs can result from the presence of Japanese knotweed growing in urban environments due to the damage it can cause to property.