A story in the Daily Mail reports that a couple from Hertfordshire were forced to demolish their £300,000, four-bed home after it was significantly affected by Japanese knotweed growth.
The cost of their new-build home was said to have dropped from £305,000 to just £50,000 as a result of the damaging effects of knotweed, on top of which the house was built.
The couple are suing the solicitors who were dealing with the purchase of the property.
Whatever you think of this story, it’s a frightening illustration that Japanese knotweed is a significant problem that needs to be recognised and professionally dealt with from an early stage of the development cycle.
Director, Dr Paul Beckett, and other Phlorum staff were invited to appear on the show offering expert advice on the treatment of Japanese knotweed at a blighted property in South London.
The knotweed problem was caused by a significant amount of growth of this invasive weed in the rear garden of the property.
A focus of the show is on helping homeowners to help themselves to deal with various building disasters. It should be borne in mind that when tackling knotweed on your own the situation can be exacerbated, sometimes catastrophically, if effective controls are not put in place and expert advice is not sought before any treatment begins.
Notwithstanding this, the advice offered by Phlorum allowed the knotweed to be cleared from the property and effectively treated, with significant cost savings to the owner.
Following the first broadcast of the show on 28th August, the feedback we’ve received from our peers in the knotweed eradication world, including surveyors, environmental consultants and contractors, has been hugely positive. This includes the following from a Fellow of RICS:
“I thought that overall the way the programme dealt with the topic was balanced and realistic and the important points were made without being too scary or over the top”.
You can catch the episode, and the whole series, on the Channel 4, 4Homes website here.
Please contact us if you would like to discuss any aspect of the show or any issues related to Japanese knotweed.
Invasive non-native species are considered a threat to biodiversity. They can cause damage to natural habitats and they compete with other plants for light, space and nutrients and often suppress native species. There is a financial cost to the economy too as substantial amounts of money are spent on containing the spread of invasive species and limiting further damage.
The first part of the report profiles 20 ‘Sites in Peril’ in the UK that are already being threatened or being damaged by non-native plants. An example of a ‘Site in Peril’ is Lundy Island. Invasive species can be particularly damaging to eco-systems when they have developed in isolation. Rhododendron is a threat to the Lundy Cabbage and is being managed by an eradication programme.
The second part of the report describes research being undertaken to try to identify non-native plants that may become invasive in the future. Examples include Himalayan knotweed; false-acacia; holm oak, and tree of heaven. Himalayan knotweed is still present in some gardens and nurseries. It grows up to two metres tall like Japanese knotweed and becomes established on stream sides, woodlands edges, roadsides, railway banks and waste ground.
Currently the invasive plants that cause the most damage to conservation sites and development sites are:
It seems an unlikely scenario but weeds can stop you getting a mortgage, or so it seems from an article in the Metro last month.
Dave Williams from Cornwall has tried to borrow £83,000 from Santander but has been turned down because of a small amount of Japanese knotweed on a piece of land that he bought recently to extend his garden. Although Mr Williams believes that had this been winter the surveyor would not have noticed, it is likely a diligent surveyor would have seen the dead canes that are evident in the winter.
He could treat the knotweed with a suitable weed killer and eventually it will die with perserverance. Patience is the key; do not be tempted to cut it back or dig it up as the roots will spread even without any leaf. If there is no building work planned on the area, it doesn’t have to be a big problem.
However, if Mr Williams is thinking of developing his garden, then he has a problem as Japanese knotweed can grow through concrete and tarmac. Currently, throughout the British Isles, it is causing the construction industry substantial financial concerns running into millions of pounds in costs to eradicate the dreaded weed.
Nettle has a new rival on the edible-weed front; Japanese knotweed, often regarded as a problem plant, has proved itself to be quite a culinary treat according to Phlorum’s Edible Japanese Knotweed Campaign in association with Brighton’s vegetarian restaurant Terre à Terre. So before you start to exterminate the plant’s, smooth, heart-shaped leaves and youthful purple streaked bamboo-like stems, consider eating away your Japanese knotweed troubles!
On a recent BBC Sussex radio appearance for the campaign, Dr. Paul Beckett claimed that if Japanese knotweed is brought under control by recently approved field trials to release a knotweed-sucking insect called Aphalara itadori then ”why not use it the same way people use other pot herbs and other native vegetation to cook with?“
The inspiration for Phlorum’s knotweed eating campaign initially arose from the inspirational work of Bun Lai, the chef and owner of Mia Sushi restaurant
who has made incredible dishes with the plant and the sharing of imaginative recipes through social networks and shared with us by Kazuyoshi Nomachi http://twitter.com/im_yutaka
Described with a flavour between asparagus and rhubarb, Japanese knotweed shoots are ready for providing a delightful tang and riveting crunch around late spring each year. Best eaten when the plant is around 6 to 8 inches tall, the knotweed can be transformed via various cooking methods such as steaming, and simmering into delicious dishes such as soups, sauces, fruit compotes and even jam. Although the plants leaves should be discarded, the rind surrounding the stalk of the knotweed can also be used to make a delightful tangy marmalade. Furthermore, besides being a delicious ingredient for cooking, Japanese knotweed provides an excellent source of vitamin A and C, along with its cofactor, the antioxidant rutin.
The plant interestingly also contains potassium, phosphorus and zinc providing the components for a very healthy ingredient.
Following Phlorum’s recent BBC radio appearance, the Japanese knotweed professionals have also been working with the award-winning Brighton-based vegetarian restaurant Terre à Terre (http://www.terreaterre.co.uk/), in order to stir up some delicious recipes with the plant.
This collaboration will also be available for viewers to watch as on Wednesday the 21st of April, a BBC South film crew will be visiting Olivia, Terre à Terre’s Events, Marketing and Design Manager in order to film Japanese knotweed delights being prepared in the kitchen and then tasted at the restaurant. Along with a TV appearance, Phlorum will also be making a further radio appearance on the same day on BBC Sussex Radio station in order to take part in the breakfast show recording of Japanese knotweed being consumed live on air with the breakfast show host, Neil Pringle.
Giant Hogweed is a non-native plant species that grows abundantly along the banks of rivers and streams. It is a member of the family Apiaceae (carrots/umbellifers), native to the Caucasus Region and Central Asia. Giant Hogweed is a perennial with tuberous rootstalks which form perennating buds each year. It flowers from late spring to mid summer, with numerous white flowers clustered in an umbrella-shaped head that is up to 80 cm (2.5 ft) in diameter across its flat top.
Hogweed is a cause for concern in that it is both a human health hazard, and exerts a negative ecological impact on infested river corridors. Giant Hogweed contains a substance within its sap that makes the skin sensitive to ultra violet light. This can result in severe burns to the affected areas, producing swelling and severe, painful blistering. Giant Hogweed is an aggressive competitor, which is able to out-compete native plant species, reducing the amount of suitable habitat available for insects, birds and mammals. Giant Hogweed produces approximately 1500 seeds per flower head in late summer. These seeds can remain inactive in the soil for several years. The movement of soil polluted with Giant Hogweed seeds must be carefully controlled to prevent the spread of the plant.
In the UK the Wildlife and Countryside Act 1982 makes it an offence to plant or cause Giant Hogweed to spread in the wild. Any Giant Hogweed polluted soil or plant material that you discard, intend to discard or are required to discard is classed as controlled waste and should be accompanied by appropriate Waste Transfer documentation.
It is characterized by its size and may grow over 2-5m tall, It is further distinguished by a stout, dark reddish-purple stem and spotted leaf stalks that are hollow and produce sturdy bristles.
Stems vary from 3-8 cm in diameter, occasionally up to 10 cm. The stem shows a purplish-red pigmentation with raised nodules. Each purple spot on the stem surrounds a hair, and there are large, coarse white hairs at the base of the leaf stalk.
The plant has deeply incised compound leaves which grow up to 1-1.7 m in width. The plant produces flattened, 1cm long, oval dry seeds that have a broadly rounded base, and broad marginal ridges.
The Giant Hogweed flowers from late spring to mid summer, and then produces numerous, large flattened elliptic dry seeds (between 1,500-100,000). Shoots die down in the autumn. Tall stems mark its locations during winter.
Control
Spraying with an appropriate herbicide such as glyphosate is the most effective treatment option available, although it can take several years to eradicate these species. The soil beneath an established stand of Giant Hogweed will contain thousands of seeds that will continue to produce new plants. Although the eradication of this species before or during construction is unlikely, herbicides can be used to achieve short-term control of the plant, allowing construction works to continue and reducing the risk to the workforce.
A catchment approach to spraying with glyphosate is required, starting at the furthest upstream site for the plant. Spraying should commence in March/early April when leaf growth has occurred and the height is >15cm. Experience has shown that seedlings are less susceptible to glyphosate treatment. A dose rate of 5 l/ha -1 is sufficient to kill treated vegetation.
Sections treated in March/April should be re-treated in May. The catchment area should be surveyed again in July and any plants that have flowered or are likely to flower must be deheaded before seeds are produced. The cut umbels must be removed from the area and destroyed. The plant should be sprayed again with glyphosate or it will attempt to flower again and set seed. A further spraying of glyphosate throughout the catchment area in September will kill or suppress the growth of autumn flowering or late-developing plants.
A quicker method of removing Giant Hogweed involves the clearing of above ground leaf/stem material and the removal of ground material polluted with roots and seeds. Due to the risk of contact with sap from this plant, removal by hand should be restricted and not considered once the plant has grown above one metre in height.
The majority of seeds that are produced fall to ground within four metres of the parent plant as they are heavy and rely on water and the wind to transport them. This four-metre radius around Giant Hogweed plants should be considered as polluted. Even with great care, a certain number of seeds may remain. A watching brief is advised after polluted ground material has been removed. Any regrowth should be treated with an appropriate herbicide as discussed above.
The two main invasive weeds that are most likely to cause problems on development sites in the UK are Himalayan balsam and giant hogweed, which are both introduced, alien species. These plants and a summary of their control options are discussed below. Also discussed below are some of the other, terrestrial plants that can cause problems on development sites.
There are also a number of introduced aquatic plant species that can cause significant problems in ecologically sensitive waterways. However, these most usually affect protected areas of conservation value that are less likely to be affected by development and for his reason they are not discussed in detail here. Defra has produced guidance on invasive species that is available for download at their website about invasive weeds legislation.
Some of the more common invasive aquatic plant species include: floating pennywort; New Zealand pygmyweed; and parrot’s feather.
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