Japanese Knotweed
What is Japanese knotweed?
With bamboo-like stems and clusters of creamy flowers, Japanese knotweed sounds exotic.
BUT...
Japanese knotweed is regarded by many people as one of the most invasive and undesirable plants in the western hemisphere. It is Resistant to most weed killers, devoid of natural enemies and capable of aggressive regrowth from a piece of root the size of a garden pea. It can flourish in any soil - however poor - spreading relentlessly, overwhelming other plants and damaging ecosystems. It has the ability to grow through walls, tarmac and concrete, thus wrecking roads and buildings.
Where did Japanese Knotweed come from and how did it get to the UK?
There are no prizes for guessing where Japanese knotweed comes from originally. Its natural habitat is on the volcanic slopes of Japan's mountain ranges, where its spread is well controlled by local pests and parasites.
Well-intentioned Victorians distributed its cuttings throughout Europe and North America and everywhere it was planted it grew vigorously. The plant is now found almost everywhere in the world, particularly beside roads and rivers and on waste ground. Its rapid and uncontrollable spread is largely down to its toughness and the fact it has no natural enemies in most countries.
The problem is now so great the government estimates that controlling the weed countrywide would cost £1.56bn. Planting it or dumping it can lead to two years in prison, a large fine, or both, under the Wildlife and Countryside Act 1981.
How It Spreads
Almost all Japanese knotweed outside of Japan is female, possibly cloned from a single introduction. In general, therefore, it does not spread through seed germination.
So how has it become such a successful invader?
The answer is in the underground stems, known as rhizomes, Rhizomes measure up to 10cm in diameter, bearing nodes at 1-2cm spacings, and extend generally up to 7 metres from the parent plant (though distances of 20 metres have been recorded). The rhizome penetrates downward to a depth of 3 metres or more each genetically identical to its parent. These rhizomes are almost impossible to eliminate. Less than a centimetre of rhizome can swiftly create a viable plant. Rhizomes were carelessly dumped in rivers and along waste ground, further spreading the weed to new localities.
The plant is characterised by dense clusters of large, heart-shaped leaves, each measuring 5-12cm wide and 5-15cm long, about the size of the palm of your hand. The plant grows from the ground in multiple woody shoots, which can be green or red in colour. The shoots grow quickly, reaching heights of between one and three metres. Very dense thickets are formed where the weed is long-established. These thickets can spread in size by a few square metres each year, displacing most other plants in the process. The multiple small white flowers, which normally appear in late August and early September, appear together in dense protruding spikes. There is a die-back in winter, but the barren shoots often remain in place throughout the season.
Environmental Damage and problems
Japanese knotweed is an undesirable plant in a number of different ways. Because of the thickness of its thickets and the density of its leaves, it prevents significant amounts of light from reaching the ground, so no other plants can grow in areas where the weed has become established. It finds most soils to its taste and propagates aggressively, displacing native flora in the process. Rare plants and overall biodiversity are threatened by this plant if it is left unchecked. The shoots can cause damage to buildings and structures, as they are capable of breaking through concrete and tarmac. Cemeteries, roads, residential dwellings and historical sites have all been extensively damaged by the plant.
The Future
Japanese knotweed is already a significant threat to gardens, buildings, roads and agricultural land throughout the western world, but the worst may be yet to come. There is a possibility that the plant could set viable seed by hybridising with related species such as the giant knotweed or Russian vine, thus enabling it to populate new areas in entirely different ways.
An infestation reduces land value and removing it is expensive and time consuming, and because even a small quantity of rhizome can cause re-growth, it is extremely difficult and very costly to eradicate through third party companies.
SLIC Training Limited are a nation-wide training provider who can offer EDI accredited training and assessment to any organisation suffering from this invasive plant, and can do so anywhere in the world.
However a SLIC Japanese Knotweed franchise would unlock the potential for your staff to eradicate Japanese Knotweed themselves making it more cost effective to your organisation over time and would mean that you would gain an in-house specialist.
The qualifications are unique and are only available through SLIC Training Ltd so contact us directly on +44 01246 505144 to release your potential.
