Lessons from Knotweed
Focussing on invasive species in this article we will look into the most problematic invasive species in the UK, the much maligned Japanese Knotweed. We will dive into it’s origins, the problems it causes and the staggering financial implication of these as well as what we can do about it including some recipes.
Japanese knotweed (Fallopia japonica,) is one of the most formidable invasive species in the UK. Its rapid growth, resilience, and ability to cause extensive damage to infrastructure and ecosystems have made it a significant concern for property owners, environmentalists, and government agencies alike. This overview delves into the numerous problems it causes, the economic costs involved, its origins and historical introduction to the UK, and its potential uses as a food source.
Problems Caused by Japanese Knotweed
Japanese knotweed is notorious for its ability to cause significant structural damage. Its roots and rhizomes (underground stems) can extend up to 3 meters deep and spread horizontally up to 7 meters. This extensive root system can penetrate and damage concrete, tarmac, and building foundations, leading to substantial structural damage to roads, pavements, and buildings. This invasive plant's presence can significantly reduce property values, making it difficult to sell affected properties. Mortgage lenders often require a professional management plan to ensure the plant's control before approving loans for properties where Japanese knotweed is present.
Japanese knotweed can grow though paving, concrete or tarmac
The environmental impact of Japanese knotweed is equally concerning. It aggressively outcompetes native vegetation, forming dense thickets that monopolise resources such as light, water, and nutrients. This dominance leads to a significant reduction in biodiversity, as native plants are unable to survive in the shaded and nutrient-depleted soil. The plant's dense growth also alters habitats, particularly along riverbanks and wetlands, increasing erosion and changing hydrological patterns. These changes can have cascading effects on the local ecosystem, affecting not just plant life but also the animals that depend on these habitats for food and shelter.
The economic costs associated with Japanese knotweed are substantial. The UK spends an estimated £165 million annually on control and eradication efforts. These costs include labour, equipment, and chemicals used in managing the plant, as well as indirect costs such as decreased property values and increased legal liabilities. Property owners can face legal action if they allow knotweed to spread from their property to neighbouring land, adding a further layer of financial risk. The Anti-social Behaviour, Crime and Policing Act 2014 provides a legal framework for fining individuals and businesses that fail to control the spread of invasive species like Japanese knotweed.
The paper - The Economic Cost of Invasive Non-Native Species on Great Britain sets out the staggering costs to the UK economy and this being 14 years ago can be considered to be much higher now.
Data from government statistics for England, Wales, and Scotland (2007/8) were used. Treatment costs vary: a 5x5 meter patch costs £20,183 to £198,200, or £800 to £8,000 per square meter (Cornwall Knotweed Forum pers. comm., adjusted to current prices). Contractor estimates range from £50 to £200 per square meter (pers. comm. in confidence). An average site cost of £5,800 + VAT was chosen (Mike Clough, JKSL pers. comm.), but total costs likely double to £11,600 per contract, including delays, legal fees, and communication.
Glyphosate - C3H8NO5P
How is it treated?
The most used method for Knotweed eradication is the use of the highly controversial herbicide glyphosate. In plants, glyphosate disrupts the shikimic acid pathway through inhibition of the enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase. The resulting deficiency in EPSP production leads to reductions in aromatic amino acids that are vital for protein synthesis and plant growth. In other words, glyphosate disrupts one of the plant’s metabolic pathways causing its death.
Natural and organic methods are simple and brutal. The only non pesticides way to deal with an infestation is in some cases to smother it with tarps or simply to dig up and burn the rhizomes, this is of course very disruptive, expensive and less effective but offers some solution for anyone not wanting to use glyphosate.,
Where did it come from
Japanese knotweed is native to East Asia, specifically Japan, China, and Korea. It was introduced to the UK in the mid-19th century as an ornamental plant due to its attractive appearance and rapid growth. The Dutch East India Company first brought it to Europe, and it was later distributed widely by German botanist Philipp Franz von Siebold. Initially appreciated for its beauty and potential use in landscaping and erosion control, it quickly became apparent that Japanese knotweed was highly invasive.
Originally imported for it looks, it now spreads fear to homeowners
Why is it not a problem in its native environment
In its native range, Japanese knotweed coexists with a variety of natural predators and herbivores that feed on the plant, helping to control its growth, these factors are not present in the UK so there is little to challenge its spread.
Various insect species, such as certain types of beetles, aphids, and caterpillars, feed on the leaves, stems, and roots of Japanese knotweed. This herbivory helps keep the plant's population in check. Specific fungi that infect and weaken Japanese knotweed are present in its native habitat. These pathogens can reduce the plant's vigor and reproductive success.
Japanese knotweed is part of a diverse plant community in East Asia, where it faces competition from a variety of native species. This competition for light, nutrients, and space limits the plant's ability to dominate the landscape as it does in non-native regions. High biodiversity in native habitats means that Japanese knotweed must compete with many other well-adapted plant species. This competition prevents it from forming the dense, monocultural stands that it often creates in invasive ranges.
The specific climate and soil conditions in East Asia are optimal for many plant species, including Japanese knotweed, but they also support a balanced ecosystem where no single species can dominate unchecked. The climate in its native range includes seasonal variations that Japanese knotweed is adapted to, but which also support other species that can outcompete or coexist with it. The soil in its native habitat contains microorganisms that interact with Japanese knotweed in ways that can limit its growth. These microorganisms can influence nutrient cycling and root health.
Over millions of years, Japanese knotweed has evolved alongside its predators, competitors, and the abiotic environment in East Asia. This long evolutionary history has led to a stable ecological role for the plant within its native ecosystem. The plant has co-evolved with its natural enemies, leading to a dynamic equilibrium where it does not become overly dominant. Predators and pathogens have adapted to feed on and infect knotweed, creating a natural check on its population.
How to use as a food
Despite its reputation as a problematic invasive species, Japanese knotweed is edible and has been used for culinary purposes, particularly in its native range. The young shoots of Japanese knotweed, which appear in early spring, are tender and have a taste similar to rhubarb. They can be used in a variety of dishes, offering a tangy flavor that complements both sweet and savory recipes. Some chef’s have described the taste as being very particular and unlike anything else, combining a sharp rhubarb tang with an earthy petrichor flavour that tastes like the smell of rain!
In terms of nutritional value, Japanese knotweed is a good source of vitamins A and C, as well as minerals such as potassium, zinc, and manganese. It also contains high levels of resveratrol, a compound known for its antioxidant properties, which is also found in grapes and red wine. This makes it not only a flavourful addition to meals but also a potentially healthful one.
When preparing Japanese knotweed for food, it's important to harvest the shoots when they are less than 20 centimetres tall. Older shoots become woody and less palatable. Knotweed should be cooked to break down its tough fibres and reduce its oxalic acid content, which can cause digestive issues in large quantities. Boiling, steaming, or baking are effective methods for preparing the plant.
This Japanese knotweed noodle dish is an incredibly Moorish recipe and what a fantastic way to do our bit and help keep an incredibly invasive species at bay, whilst enjoying a top-notch meal.
To make enough to feed 2 people
INGEDIENTS
2 stalks Japanese knotweed, slice across to make circles of knotweed
100g dried rice noodles (I like 3mm but choose the thickness you like)
1tbsp soy sauce
1tbsp kimchi (use your favourite but we love the wild garlic kimchi from kimchi radish in London)
1 small shallow – diced
2 mushrooms – diced (Oyster works well but button mushroom are fine too)
50g Edemame Beans
Some spring onions & knotweed for garnish
METHOD
Pop the noodles in a jug and top up with boiling water (approximately 500 – 700ml to cover them and leave for 5 minutes to hydrate
Fry off the Mushrooms & onion in a pan for 3 minutes with a little oil
Add in the hydrated noodles and the liquid from them also
Chuck in the rest of the ingreients until warm (a couple of minutes)
top with some raw knotweed slices and some spring onions diced and enjoy
For more detailed recipes have a look at the Totally Wild website
Lessons for humanity
The situation with Japanese knotweed offers profound philosophical lessons about the balance of nature, the consequences of human actions, and the importance of understanding and respecting ecosystems. It underscores the interconnectedness of ecosystems and the delicate balance that sustains them. This case illustrates the holistic nature of ecosystems, where every species, from the smallest microorganism to the largest predator, plays a role in maintaining balance. Disrupting one element can have far-reaching consequences, highlighting the interdependence of species, as plants, animals, fungi, and bacteria form complex relationships that sustain the environment.
The spread of Japanese knotweed exemplifies the law of unintended consequences, where human interventions in nature can lead to unforeseen and often detrimental outcomes. This calls for a more thoughtful and cautious approach to our interactions with nature. The introduction of Japanese knotweed was initially well-intentioned but lacked foresight regarding its long-term impact. Humanity must recognise its role as stewards of the planet, bearing responsibility for both protecting and preserving the natural world.
The difficulty in controlling Japanese knotweed reveals the limitations of human knowledge and our ability to manage nature. This teaches us to be humble about our understanding of complex ecological systems and cautious about assuming we can control them without negative repercussions. It encourages an adaptive mindset, where learning from mistakes and continuously improving our approaches to ecological management is crucial.
The impact of Japanese knotweed on biodiversity emphasises the intrinsic value of diverse ecosystems. Biodiversity should be valued not just for the benefits it provides to humans but also for its own sake. Every species contributes to the richness of life on Earth. This calls for an ethical approach to conservation that respects the intrinsic worth of all living beings and the ecosystems they inhabit.
The need to manage invasive species like Japanese knotweed reflects the broader challenge of achieving sustainable coexistence with nature. This suggests a philosophical shift towards living in harmony with nature, recognising that human well-being is deeply interconnected with the health of the planet. It promotes long-term thinking and planning, considering the impacts of our actions on future generations and the environment.
The story of Japanese knotweed serves as a reminder of the profound wisdom embedded in natural ecosystems and the philosophical insights they offer. It calls for a deeper respect for the complexity and interconnectedness of life, a recognition of the limits of our control, and an ethical commitment to stewardship and sustainability. By learning from these insights, humanity can strive to make more informed, thoughtful, and respectful decisions regarding our relationship with the natural world.