One of the common problems with invasive weeds is identifying them. There are countless tales of people blithely strimming back a stand of knotweed and spreading it because they didn’t recognise what they were dealing with. Hopefully this has become less common in recent years due to increased publicity and awareness of invasive species issues but it does still happen.
Once you know what you’re looking for you’ll spot Japanese Knotweed everywhere you look and Giant Hogweed, as the name suggests, grows large enough that it’s difficult to miss. A word of advice though, you don’t have to mention it every time you spot some, your friends and family will begin to mock you.
But what if the plant doesn’t look like it’s expected to?
Various things can affect the growth and development of plants, limited light, limited water supply, limited nutrients or phytotoxic contaminants in the soil and as in this case treatment with a herbicide. This is particularly important with Japanese Knotweed which will require a course of treatments over several years so you can expect to encounter these effects.
The picture above shows a stand of Japanese Knotweed which has previously been treated with a glyphosate based herbicide. As a result of this when regrowth which has occurred the entire stand is smaller and less vigorous than previously. Despite being smaller and somewhat distorted most of the plant is recognisable as knotweed, however the circled plant in the central foreground of this photo does look distinctly different. This is what is termed as Bonsai Knotweed because of the miniaturised and twisted appearance of the plant. If there was only bonsai knotweed present on the site it would be rather easy to mis-identify it as something less troublesome. The knock on effects of such a failure to identify knotweed could be costly and may even lead to breaches of the law.
On the plus side this form of growth for knotweed is distinctive of a stand which has regrown after treatment so it’s likely that the course of treatment will be scheduled to continue. But if in doubt, particularly if you’re intending to develop the area where this plant is growing, it’s wise to contact a professional to have a look.
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