How to spot invasive Japanese knotweed during autumn as Brits issued warning

During autumn numerous changes occur, from dropping leaves to lengthening nights and plummeting temperatures.

Whilst many consider gardening a spring or summer activity, there are considerable advantages to monitoring plants throughout other times of the year as well. One species that alters as autumn advances is Japanese knotweed (Fallopia japonica), an invasive weed.

This experiences remarkable changes that make identification simpler. The most noticeable transformation occurs in its foliage, which transitions from summer green to hues of yellow and orange.

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JapaneseKnotweed.co.uk says: "By September and October, these leaves begin to wilt and fall, creating a dense layer of foliage on the ground. This colour change and leaf drop are significant markers of the plant's seasonal cycle."

Additional characteristics to watch for include the stem, according to the specialists: "In addition to changes in the foliage, the plant's stems also transform. The once green, speckled stems turn brown and remain hollow, similar to bamboo."

"As the leaves fall away, these brown canes become more distinguishable, standing out starkly against the autumn landscape. This combination of yellowing leaves, wilting foliage, and prominent brown stems provides a clear indication of Japanese knotweed during the autumn months, aiding in its identification and management."

This summer's balmy weather has provided the perfect breeding ground for Japanese knotweed, with over 100,000 infestations now recorded annually in the UK, reports the Liverpool Echo.

Originally introduced as an ornamental garden plant, this persistent herbaceous perennial has since morphed into a legal nightmare, spreading its invasive tendrils far and wide since its introduction in 1850.

Despite being most visible during the flowering season, this aggressive plant can be spotted even in the colder months, ready to wreak havoc on gardens if left unchecked.

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With its relentless drive to reproduce, Japanese knotweed is currently affecting over 1.5 million households across the UK, either directly or through neighbouring properties. Even as the stems start to die back in autumn, the underground system remains primed for regrowth.

TheRoyal Horticultural Societyhas clarified: "It is not an offence to have Japanese knotweed growing in your garden, but it is an offence to plant it or cause it to grow in the wild and you should take steps to prevent it spreading. Additionally, a relevant environmental authority can order control measures if they deem such action necessary."

The RHS suggests that the easiest way to eradicate these invasive weeds is to hire a professional company specialising in their removal.

An environmental authority can offer advice for mortgage purposes, including proposed treatment plans, and provide insurance-backed guarantees if needed. You should avoid adding Japanese knotweed to your home compost. If home composting isn't feasible, many local councils run green waste recycling schemes.