The Beauty of The Beast in The East

29th July 2022

Watch Out For 'aggressive and destructive' Japanese Knotweed.

Japanese knotweed is a potent, fast-growing, invasive weed with tall, dense stems. Although the plant dies back to ground level in winter, the bamboo-like stems can grow over 7ft tall by early summer. 

For homeowners, the plant can pose serious problems if left unchecked, with the potential to grow through cracks in concrete, tarmac driveways, pathways, drains and cavity walls. In the UK as a whole, Environet estimates that Japanese knotweed currently affects 5% of UK properties wiping £20 billion off house prices. Those properties affected by the invasive plant often see their property value drop by around 10% due to its fast growth and destructive nature.

Not only can it depreciate the value of a house, but it also deters buyers in general, and sellers are required by law to inform any potential purchasers about whether the house has been affected by Japanese knotweed.

Last year Walthamstow was named the third biggest hotspot for Japanese knotweed in London and the worst east London area for the damaging weed. 

This year Tottenham (219) and Leytonstone (206) ranked in the top five worst spots in London for Japanese knotweed. 

Knotweed occurrences within a 4 km radius of Walthamstow this year are 201, Plaistow 145, East Ham 180, Forest Gate 196, Highams park & Chingford 136 and Hackney 99.

Currently, there are almost 55,500 known occurrences of the UK’s most invasive plant.
 

How to spot Japanese Knotweed

In Spring, new growth emerges as rapidly growing soft red/purple shoots reminiscent of asparagus spears. The stems are hollow and bamboolike and can grow up to 10cm daily. This new growth forms dense thickets known as stands. The leaves grow on alternate sides of the stem producing a zig-zag pattern in the stem.

In Summer, the plant will flower, producing elongated clusters of small creamy-white flowers.

In Autumn, the dense covering of leaves will remain; however, they start to turn yellow and wilt as we move into September and October. The knotweed plants are still about 2-3 metres tall, and the hollow stems start to turn brown. 

In Winter, the canes die off and turn brittle. The crown and rhizome remain dormant throughout the winter. Winter stems are brittle but can remain erect through winter if left undisturbed and unaffected by inclement weather.
 

What To Do if You Have Japanese Knotweed on Your Property?

The first step to tackling the plant is to commission a professional Japanese Knotweed survey and find out the extent of the infestation. They will be able to tell you where it originated and the best way to tackle it.

If left untreated, Japanese knotweed can quickly take over your garden. Its roots cannot simply be pulled out, and professional attention is typically required in order for the root system to be removed effectively. 

There are three ways to treat and remove Japanese knotweed.
 
1) Spray it with chemicals - One effective way to stop knotweeds from spreading is by spraying or injecting the stems with chemicals. However, it is crucial only to use approved pesticides.

2) Bury the knotweed - If you plan on burying the Japanese knotweed, you must notify the Environment Agency at least one month prior. It is possible to dispose of the dead brown canes of the knotweed by composting on site, but you must make sure they're cut (not pulled) a minimum of 10cm above the crown.

3) Burn it - Suppose you are a business which wants to burn Japanese knotweed. In that case, you must tell the Environment Agency at least a week before, tell the environmental health officer at your local council, get a burning waste in the open exemption and follow local byelaws to not cause a nuisance.

If you are an individual who wants to burn Japanese knotweed, it is only necessary to check with your local council that burning is allowed.

Be aware that knotweed crowns and rhizomes might survive burning, so you need to follow instructions on how to bury them or dispose of them off site afterwards.