Complete Guide to Japanese Knotweed Removal

This guide provides in-depth information on identifying Japanese knotweed and the professional removal process to eliminate infestations.

What is Japanese Knotweed?

Japanese knotweed (Fallopia japonica) is a large, herbaceous perennial plant that is native to East Asia in Japan, Taiwan and northern China. The Royal Botanic Gardens in Kew introduced it to the United Kingdom in 1850 as an ornamental plant. It has since become an extremely aggressive invasive species, particularly prevalent in London and South Wales.

Physical Characteristics

Japanese knotweed has distinctive physical features:

• Hollow, bamboo-like stems – The mature stems are green in colour and hollow inside with nodes separating each stem section. They closely resemble bamboo shoots and range from 0.5 metres to a maximum of around 3 metres tall at maturity.
• Shovel or heart-shaped leaves – The leaves are shovel or heart-shaped with a pointed tip. The size ranges from 5-15 cm long by 3-10 cm wide. They emerge from zig-zagging branches where the leaves join the main stem.
• Dense clumps – The plant grows in dense clusters or thickets from a central crown, with multiple stems shooting up together in close proximity from an extensive underground rhizome root system.
• Small white flowers – In late summer through early autumn it produces numerous small white flowers on arching stems, sometimes described as looking like strings of pearls on the upper stalks. The flowers are around 5mm in diameter.

Growth Habits

Japanese knotweed exhibits rapid, resilient growth:

• Rapid early growth – In spring it has an accelerated growth phase, capable of growing up to 10cm per day in ideal conditions. It can achieve heights of 2-3m high by mid-summer.
• Spreads laterally – The plant grows vertically rapidly and extends laterally. Each year the underground roots and rhizomes can expand up to 7 metres horizontally outward from the parent plant.
• Resilient rhizome roots – The plant has a vast underground root system comprising rhizomes and roots that can extend down to 3m deep and spread laterally up to 20m from the visible growth above ground. The rhizomes store energy reserves which fuel the rapid regrowth each spring.
• Regrows vigorously – The above-ground stems and foliage die back each winter but the underground crown and rhizome roots remain alive and protected in the soil. This allows fresh new spears to reshoot vigorously each spring from the existing root system.
• Displaces other plants – Due to its dense growth habit and rapid spread it tends to displace and shade out other plant species, reducing biodiversity in infested areas. It forms dense single-species stands and thickets that dominate sites.

So in summary, Japanese knotweed is characterized by its bamboo-like hollow stems, distinctive shovel-shaped leaves, rampant vigour, rhizome root system, and ability to spread rapidly to form invasive thickets. These traits enable it to cause significant damage.

Legal Status and Need for Removal

Due to its destructive invasive impacts, Japanese knotweed is classified as controlled waste and subject to legal restrictions under UK law. There are compelling reasons removal is necessary.

Legal Classification

• Japanese knotweed is listed under Schedule 9 of the Wildlife and Countryside Act 1981 as an invasive non-native plant species.
• It is categorised as ‘controlled waste’ under the Environmental Protection Act 1990.
• The Environmental Protection Act identifies Japanese knotweed as a ‘controlled waste’ because of its potential to cause structural damage, harm ecosystems and spread rapidly if not correctly disposed of.

Implications

• It is unlawful for homeowners and landowners to allow Japanese knotweed on their property to spread to adjoining land or watercourses where it may take root, grow and cause damage.
• Property owners have a legal duty to prevent Japanese knotweed spreading from their land. Failure to control infestations can lead to prosecution and fines of up to £5,000 under the Anti-Social Behaviour, Crime and Policing Act 2014.
• Local authorities can serve injunctions forcing landowners to properly manage infestations under the Environmental Protection Act 1990 provisions.

Property Impact

• Japanese knotweed can cause serious physical damage to properties. As well as undermining foundations, it can push through cracks in walls, pavements, drains and cause major damage.
• Japanese knotweed can make a property difficult to sell, mortgage or re-mortgage. Most mortgage lenders will not provide loans without professional knotweed treatment to satisfy lending criteria.
• Infestations can devalue affected properties by around 5-15% on average due to the damage risks and concerns over selling on.

So in summary, the classification as controlled waste, property damage risks and difficulties selling or borrowing against affected properties mean there is a clear legal impetus and financial incentive for landowners to tackle Japanese knotweed through professional removal.

Identifying Japanese Knotweed

Correctly identifying Japanese knotweed is critical before undertaking removal, as misidentification could lead to eliminating desirable vegetation unnecessarily. Unique identification features to look for include:

Above Ground Growth

• Hollow green stems – Mature knotweed stems are hollow and bamboo-like when you split them open, with a characteristic central cavity. They are green with reddish-brown mottling.
• Shovel-shaped leaves are typically a shovel or heart shape, around 5-15cm long and 3-10cm wide. They taper to a point at the end.
• Zig-zag branches – The leaves join the main stem in an alternating zig-zag pattern. This gives knotweed shoots a very distinctive look.
• Small white flowers – In late summer through early autumn, numerous tiny creamy-white flowers appear in dangling clusters on arching branches, sometimes described as resembling strings of pearl beads.
• Rapid early growth – Shoots can grow up to 10cm per day in spring. This rapid early-season growth helps distinguish knotweed from other plants.
• Dies back in winter – Unlike shrubs, herbaceous knotweed dies entirely in winter, leaving only hollow brown stems and root crowns.

Below Ground Rhizomes

• Extensive underground roots – Japanese knotweed has a vast rhizome root system extending up to 7m deep and 20m laterally underground. Even if no visible growth is apparent, roots may still be present.
• Difficult to eradicate – Removing the plant without the rhizome roots leads to rapid regrowth. This makes professional excavation of root systems necessary for full eradication.

Confirming Identification

If identification remains uncertain, specialists can perform:

• Lab analysis – Samples taken to labs for microscopic comparison to reference specimens.
• DNA testing – Detects specific genetic markers that confirm Fallopia japonica conclusively.

So in summary, a combination of tell-tale visible traits and analysis of underground rhizome roots enable definitive identification of invasive Japanese knotweed for removal purposes.

Professional Removal Methods

Specialist contractors have several effective treatment options to tackle Japanese knotweed, which are often used in combination:

Herbicide Treatment

• Glyphosate-based herbicides – Systemic glyphosate is the most common herbicide used. It is absorbed by the leaves and translocated down to the roots.
• Foliar spraying – Sprayed directly onto the leaves and stems during active growth periods. Provides wider coverage.
• Stem injection – Herbicide injected into each plant stem using special applicators. More targeted application.
• Repeated application required – Typically requires at least 2-3 years of repeated applications to eradicate established rhizome root systems fully.
• Licensed contractors only – Due to the risks, herbicide application should only be conducted by certified specialists licensed by the government environment agency.
• Correct timing critical – Applications must coincide with certain growth stages to ensure optimal absorption and translocation down to the rhizome roots.

Excavation

• Mechanical digging – Uses excavators and other machinery to dig out infested soil.
• Must remove rhizome roots – Soil must be excavated to a minimum of 1 metre beyond visible above-ground growth, up to 3-5 metres for extensive rhizomes.
• Offsite disposal – All contaminated soil and plant material should be disposed of at a licensed Japanese knotweed treatment facility.
• Extensive repairs required – The excavated area will need extensive backfilling, reprofiling, replanting and landscaping.

Root Barrier Membranes

• Impenetrable membranes – Usually a thick, high-density plastic or geotextile membrane dug vertically into the ground.
• Contain spread – The barrier walls off rhizome growth and contains the infestation footprint, preventing further extension.
• Often used with other treatments – While effective for containment, root barriers do not eradicate, so are often used alongside herbicide or excavation.

Combined Approach

• For optimal results, integrating herbicide treatment and excavation tackles the weed both above and below ground far more comprehensively than either method alone.

So in summary, while options like herbicide application, excavation, and barriers all have merits, using professional contractors experienced in integrated treatment plans provides the most robust long-term management.

Step-by-Step Removal Process

The typical removal process involves:

1. Initial professional knotweed survey
   
   • A qualified invasive weed control specialist will thoroughly survey the infested area to identify all locations of visible growth and map root spread.
2. Site preparation
   
   • The area will be prepared by clearing access routes, erecting fencing if needed, and preparing storage areas for excavated materials.
3. Herbicide treatment
   
   • A specialist contractor will apply appropriate herbicides in accordance with regulations. Typically, glyphosate is used, applied 2-3 times over the growing season.
4. Excavation
   
   • Once the herbicide has killed the knotweed growth back, the root system and contaminated soils will be excavated using machinery. Excavation is done carefully to remove all traces of roots and rhizomes.
5. Controlled waste disposal
   
   • The knotweed plant material and soils will be disposed of at a licensed landfill site in accordance with waste regulations.
6. Root barrier installation
   
   • A root barrier membrane approved for invasive plant containment is installed to line the excavated area and prevent regrowth from outside.
7. Import topsoil and replant
   
   • Clean, weed-free topsoil is imported to fill the excavated areas and allow replanting of desired vegetation.
8. Follow-up herbicide treatments
   
   • Occasional follow-up herbicide treatments may be required if any regrowth occurs from roots or plant fragments remaining in the soil.
9. Post-treatment survey
   
   • Once eradication work is complete, a further detailed survey is done to confirm success and check for any remaining growth.
10. Ongoing monitoring
    
    • The treated area should be monitored for at least 3 years after treatment to ensure no regrowth, which can then be quickly retreated.

Why Use Professional Contractors?

Hiring professional specialist contractors rather than attempting do-it-yourself removal is highly recommended when dealing with large-scale weed infestations. Professional contractors have extensive expertise and resources that homeowners do not.

Expertise

Contractors have specialist knowledge in identifying different types of invasive weeds and determining the most effective treatment methods for complete eradication. They stay up-to-date on the latest regulations regarding herbicide use and waste disposal.

Resources

Contractors have access to heavy equipment and machinery required for large-scale excavation and removal work. Attempting extensive digging without proper tools risks injury and damage.

Treatment Knowledge

Professionals know which combination of mechanical removal, herbicides, and follow-up treatments works best for eliminating different weed varieties. Correct identification and treatment is critical to preventing regrowth.

Compliance

Contractors follow all legal regulations for herbicide use and waste disposal, avoiding unknown fines or violations homeowners could face. They have the proper licenses and permits.

Insurance & Guarantees

Reputable contractors offer guarantees against weed regrowth for 1-3 years. They have liability insurance protecting homeowners in case of property damage.

Complete Eradication

With their expertise, equipment, and systematic treatment, professionals can fully eradicate weed infestations and provide certification of removal. This prevents recurring growth.

Hiring professional contractors is the safest and most effective approach for large weed control and removal projects. Their knowledge and resources lead to long-term solutions homeowners cannot achieve alone.

Conclusion

Left unchecked, Japanese knotweed poses severe property threats through damage and devaluation. Professional removal using integrated herbicide and excavation techniques provides the most robust and reliable solution to eliminate infestations and prevent regrowth. Working with certified specialists ensures legal compliance and offers guarantees against future regrowth.