One of the common problems with invasive weeds is identifying them. We carried out some research with YouGov in 2018 that showed fewer than one fifth (19%) of Brits who said they were aware of Japanese knotweed could correctly identify it.

Every day, especially at this time of year, people across the country are blithely strimming back a stand of knotweed and spreading it because they didn’t recognise what they were dealing with.

When it comes to bonsai knotweed, however, the proportion of people who would be able to successfully identify it becomes even smaller. Regrowth of Japanese knotweed which has been treated with herbicide can look very different to the healthy plant. It tends to grow back with straggly stems, small leaves and no flowers, seldom reaching heights in excess of 50cm, compared to the 3 metres reached by healthy plants.

It’s easy to see why people who attempt to treat knotweed themselves using over the counter weed killer such as Roundup, are led to believe they’re getting somewhere. The plant does re-emerge the following spring but is so dramatically diminished in appearance, that they believe they are winning the battle.

But what they can’t see, unless they dig and keep on digging, is that the rhizome or root system beneath the ground is still alive and well. This is the part that can and will cause major problems in the future unless it is completely removed.

Bonsai knotweed simply isn’t large enough to take in the required volume of herbicide to kill the rhizome beneath the ground, therefore the best course of treatment is to excavate it to ensure there is no trace of viable rhizome remaining in the ground. To find out more about excavation please visit our Resi Dig-Out™ page.

If you’re not sure what you’re dealing with, you can send a photo of a suspicious plant to [email protected] and we’ll let you know what it is, free of charge.