Japanese Knotweed vs. Bamboo: Which is the Most Invasive Species?

Japanese knotweed and bamboo have many things in common: they’re both ornamental plants and they’re also incredibly invasive. Unfortunately, when left to grow and spread, these plants are responsible for considerable damage, amounting to thousands in repairs for homeowners and taxpayers.

Allowing Japanese knotweed to spread into neighbouring properties or the countryside could also carry significant fines and penalties. It’s so invasive it’s been known to kill other ecological systems and destroy vegetation plots. Whilst there’s no legislation in place to control bamboo, it is also capable of causing structural damage to buildings. That’s why, it’s more important than ever to get these plants under control and ensure they can’t spread.

Japanese Knotweed vs Bamboo: Why Are They Invasive?

Despite their ornamental appeal, both Japanese knotweed and bamboo can cause serious damage in and around the areas they grow. Unfortunately, their ability to spread, as well as their tough and thick root structures, make them both invasive species.

It’s true that bamboo and Japanese knotweed have been popular fixtures within domestic gardens, and we can thank the curiosity of the Victorian upper classes for this alone. During the Victorian era, understanding new species, as well as botany and plant cultivation, piqued the interest of many households. And, just like a fashion trend, as the plants were displayed to family, friends and fellow aristocrats, their popularity grew.  

What are the Differences Between Japanese Knotweed and Bamboo?

As invasive species, Japanese knotweed and bamboo have some stark similarities and differences. Although they can both wreak havoc on homes, ecological systems and vital infrastructure, they also have key distinctive features to help tell them apart.

Japanese Knotweed

Stems

Upon a quick glance, the stems of a Japanese knotweed plant might appear like those of a bamboo. As it grows to full size, the stems also feature ridges and a slight zig-zag growth pattern as bamboo.

Flowers

Alongside their shovel-shaped leaves, Japanese knotweed plants are accompanied by clusters of creamy white flowers. These typically come through in the summer months, with the plants in flower around August to September months. The flowers are also quite similar to those on Himalayan knotweed.

Leaves

Described as either heart or shovel-shaped, the leaves on a Japanese knotweed plant differ from those shown on bamboo. With a much wider surface area, the plant’s leaves are also a much darker green in comparison. Japanese knotweed also loses its leaves in the autumn and winter months.

Shoots

The shoots of a Japanese knotweed plant look slightly like asparagus spears but can be easily told apart by their colouring. Infant Japanese knotweed is often a reddish-brown before it develops. Typically, Japanese knotweed tends to grow where hollow or dead stems lay on the ground.

Roots

Strong and often clustered, the roots of a Japanese knotweed plant are also known as rhizomes. They are hardy enough to grow almost everywhere and can appear tough as they cluster under the ground. As the plants are invasive, they only require 0.2g of their rhizome to survive a culling, meaning they can easily grow again.

Bamboo

Stems

One of the most notable characteristics of a bamboo plant is its stems. Cylindrical in shape, the stems also feature small ridges which are also known as nodes, and are designed to strengthen the stem as it grows.

Flowers

Flowering on a bamboo plant is quite a rare occurrence and can happen once every 65-120 years. However, this frequency is dependent on the species of bamboo growing. Bamboo plants known to flower, such as clumping or running bamboo, also drop their seeds during different seasons.

Leaves

One of the most notable differences between the two plants is the leaf structure. Bamboo has narrower leaves compared to Japanese knotweed. They descend into a pointed shape that is similar to grass and are normally symmetrical. Unlike Japanese knotweed, bamboo normally retains its leaves.

Shoots

Despite their pointed tips, the base of bamboo has more girth compared to that of Japanese knotweed. Its exterior is best described as woody and thick, preserving it as it grows. What’s more, bamboo shoots are often harvested and enjoyed as Asian cuisine.

Roots

Bamboo roots can spread evenly and can grow up to 20 feet away from the main base of the plant. Unfortunately, this can mean damage to nearby properties or infrastructure as they can easily grow beneath driveways and house foundations. That’s why bamboo root structures need to be checked frequently and treated if required.

How Were They Introduced to the UK?  

It’s no surprise that we have our Victorian ancestors to blame for introducing both plants to the country. However, they crossed British waters and entered domestic properties within different decades.

Japanese Knotweed’s Introduction to the UK  

As European countries explored more Asian territories, they brought back certain marvels that didn’t exist within British culture or British life. These fascinations, especially for botanical studies, led to the plant being introduced in 1850 by a German botanist.  

Japanese knotweed had already made a name for itself three years prior in The Netherlands being coined “the most interesting new ornamental plant of the year” by the Society of Agriculture and Horticulture. Of course, hindsight is a great thing.

Bamboo’s Introduction to the UK

Almost 25 years prior to Japanese knotweed crossing British waters, bamboo arrived at Kew Gardens in 1826. During the Victorian era, there was a huge obsession for plant-hunting with keen botanists eager to introduce new species, learn them and understand their anatomy.  

Introducing this species was trial and error. Botanists couldn’t determine whether the plant would survive the climate or thrive within the soil. At the time, it was sent to separate centres and places within the country to see if it could survive.

What Damage Has Been Caused By Japanese Knotweed and Bamboo?

Unsupervised and unchecked invasive plants have a tendency to cause major disruption and damage. From overhead cabling to building foundations, Japanese knotweed and bamboo are notorious for costing taxpayers in excess of £246.5 million each year. In fact, Japanese knotweed is the most expensive invasive species on Britain’s shores.  

Japanese Knotweed Damage

Japanese knotweed is strong enough to penetrate cracks in foundations and can grow through them, causing damage to walls, properties and infrastructure. It’s strong enough to gradually lift paving slabs, creating trip hazards for visitors or walkers. What’s more, it can also cause blockages in drainage pipes as it’s capable of growing and spreading underground.

Bamboo Damage

Introduced as decorative plants for the garden, bamboo can also wreak havoc on a domestic property. Not only can it push through any cracks or gaps in bricks, causing damage to driveways and foundation walls, but it has also led to an increase in nuisance claims for mortgage lenders. It has the potential to restrict lenders from supplying mortgages for properties infested by bamboo.

What Legislation is in Place?

Bamboo Legislation

Unlike Japanese knotweed, bamboo is not covered under any legislation making it neither illegal to own or allow the plant to spread. However, that doesn’t mean its consequence free. Some households have reported the plant costing them damage in excess of £100,000. It’s believed that some mortgage lenders may also restrict borrowing if your home is infested with bamboo.

Japanese Knotweed Legislation

Although it’s not illegal to have Japanese knotweed on your property, it is illegal to allow it to spread out to neighbouring properties. As the plant causes significant damage, if you allow it to spread and are unable to control it, you may be liable under the Wildlife and Countryside Act 1981, as well as the Anti-Social Behaviour, Crime and Policing Act 2014 and the Environmental Protection Act 1990.

How Should Japanese Knotweed and Bamboo Be Removed?

For proper removal and disposal, it’s always best case to employ specialists. Invasive plant specialists are able to fully manage and assess the threat both Japanese knotweed and bamboo pose. In many cases, they may also offer a guarantee in the event regrowth happens.

Depending on the level of infestation and how much soil has been contaminated, there are a number of possibilities when it comes to the removal of both plants. They should be meticulously and cautiously removed to avoid their respreading. For example, Japanese knotweed plants can thrive when just 0.2g of rhizome is left behind.

Methods for removal may include:

• Excavation tactics
• Burning
• Herbicide and spraying
• Off-site removal (with a licenced carrier)

Think You Might Have an Invasive Species on Your Property?

If you believe either bamboo, Japanese knotweed or buddleia is growing on your property, you may want to take action sooner rather than later. At Japanese Knotweed Specialists, we’re able to identify, risk assess and remove both plants, whilst offering you a guarantee in case of regrowth. Contact us today.

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