Japanese knotweed is like the house guest who just won’t leave. It’s not easy to get rid of and can come back uninvited. Once treated with herbicides, however, it’s gone for good ... Or is it?
Can Japanese knotweed return after treatment?
Yes, it is possible for Japanese knotweed to return after treatment. This is because herbicide treatment doesn’t actually kill Japanese knotweed, but leaves the root dormant and depleted of energy. Having said that, Japanese knotweed won’t usually come back unless the depleted root is moved in some way.
A bit like a genie in a lamp, the once-sleeping Japanese knotweed root need only be disturbed to burst into life and cause trouble. For example, extending your house into your garden or doing extensive landscape work could cause a new outbreak. If only it granted wishes!
Annoyingly, Japanese knotweed can lay dormant below ground for up to twenty years before it finally loses its ability to re-grow. Even worse for those in a financial pinch, Japanese knotweed is more likely to return if it’s been treated DIY-style.
DDIY - Don't treat knotweed yourself
When you treat Japanese knotweed yourself you simply won’t be equipped with the right solutions, equipment and knowledge to do an effective job. We’re not trying to dampen the spirits of DIYers out there, but most DIY attempts only make the plant look dead and, sometimes, make it spread further. Here’s how.
Japanese knotweed growth
Japanese knotweed leaves
Knotweed hiding amongst garden plants
Mishandling
When you mishandle Japanese knotweed you encourage it to spread. In fact, when a small fragment falls or chips off the plant it has the capacity to start a new growth where it lands. It’s not coughs and sneezes that spread diseases in our gardens, but bits and pieces of invasive species!
So, when you try to treat Japanese knotweed, especially with weak-grade herbicides, you could easily be helping it to spread around your garden. You might find it popping up in random places.
Weak weed killer
Weedol and Roundup are generally ineffective against Japanese knotweed. And while they and many other shop-bought weed killers work well for other prickly problems, they are not strong enough to stop knotweed growing.
And yes, the plant may look dead if you treat it with Roundup (i.e., the leaves and stems may look burnt and brittle) but it’s not dead. It’s only playing dead because the plant’s energy hides away deep underground in its root.
Ineffective spraying
Spraying Japanese knotweed with herbicides isn’t as simple as it seems. It must be done at certain times of the year and usually over the summer for several or more years.
Spraying the plant randomly will not help and some infestations may need stem injection to protect surrounding flora and fauna from herbicide-related poisons. Let’s not poison our lovely waters and kill all the fish!
Incorrect disposal
Similar to mishandling Japanese knotweed, incorrectly disposing of it could generate a new growth. It’s actually against the law to put it in your garden or household waste bin. This is because it’s considered contaminated waste under the Environmental Protection Act 1990.
Oh – and never put Japanese knotweed in your compost bin. It will have the time of its life.
In fact, to fully protect your garden from an outbreak, Japanese knotweed pieces should be taken to a licensed landfill centre via a registered waste carrier vehicle. Normally, knotweed professionals will do this on your behalf.
Knotweed Growing in UK Gardens
Japanese knotweed sprouting in residential garden
Japanese knotweed growth
Get knotweed treated professionally
We’ve made treating Japanese knotweed with herbicides look useless. But that’s not always so! Knotweed that has been treated professionally is unlikely to rear its ugly head.
This is because specialists have access to high-grade herbicides, plant equipment and a working and scientific knowledge of the plant’s behaviour. Professionals will also spray or inject the knotweed over a set period of time depending on the infestation.
All in all, hiring experts to treat your Japanese knotweed is the best way to stop the pest returning!
That much-needed guarantee
Any Japanese knotweed removal company worth their name should, after they have treated the infestation, offer you an insurance-backed guarantee (or IBG). This document is essential. An IBG is a promise to you, the homeowner. It means that should the knotweed return to your land then the professionals will also return to re-treat or excavate it.
So, in the very unlikely event that a re-growth appears, you’re legally and financially covered. An IBG document will also help when you move home. At least, it makes communicating with dreaded solicitors that much smoother!
If you’re dealing with knotweed, professional treatment is the safest (and easiest) long-term solution. Give our friendly team a call to discuss treatment plans on: 0330 678 1077
