What is Japanese knotweed?
Japanese knotweed is a non native invasive plant. This means that it is not natural to the UK and grows at a prolific rate with little stopping it. It originates from Japan and is considered a beautiful ornamental plant with excellent fast growing properties. The Victorians picked up on this and brought it over to England.
However 150 years on, there is little which naturally kills it or at least keeps it at bay. The roots grow up to 7 metres from the original plant and then further stems appear. The roots can grow to a significant depth, which is why there is so much concern about the affect it has on foundations of properties.
What does Japanese knotweed look like?
The stems are bamboo in appearance
Dead canes give a satisfying "pop" when you snap them.
The leaves are NOT heart shaped at the top but flat, at the tip they are heart shaped.
The leaves look more like a small gardening spade shape, pointy at the end but flat at the top.
The stem where the leaves come off are zig-zag in shape
The root snaps like a carrot.
It can grow approximately 10cm a week in the summer.
Can i just dig it out?
NO! Digging it out generally spreads the problem!
Unless you want to remove the soil sometimes to a depth of 3metres and 7metres from the original plant, where it can be guaranteed that the plants and root have been removed.
Do seek professional advice before choosing this option.
Can i just cut it down?
Cutting in the short term (this gives you about a week in high-season) removes all visible shoots and stems, but the roots simply produce more stems or grow up somewhere else which is easier to grow.
Many customers often report to us that they have cut it down for many years, but its just getting out of hand, rather than removing the problem, it’s become far worse.
Treating the Japanese knotweed as soon as possible is the cheapest and most cost effective method.
The other problem with simply cutting it down or digging it up is it is illegal to knowingly transport or remove Japanese knotweed – as a little as the size of a penny can grow quickly into a new plant, which is the main reason it is so invasive!
Where has the knotweed in my garden come from?
Many of our customers have no idea where the knotweed has originated from.
From our experience it will have originated from elsewhere but been cut and transported to your property from mainly human activity such as builders’ waste, contaminated compost as well as other sources.
I’m worried as its flowering – will all the seeds grow into new shoots next year?
Nearly all the Japanese knotweed in the UK presently is female (with the exception of a few sites) so you don’t have to worry about the pollen from the flowers producing more Japanese knotweed.
It may cross fertilise but currently the plants produced from this are nothing as fierce as Japanese knotweed. This means that the plant is transported through the cutting and regeneration rather than through pollen or seeds.