Picture of Japanese Knotweed and how to identify it

Plants Often Mistaken for Japanese Knotweed

Japanese knotweed is a peculiar plant, It can be hard to figure out if you actually have this highly invasive species growing in your garden or on an area of a commercial property. It's not always possible to immediately identify Japanese knotweed, and indeed there are many plants commonly mistaken for Japanese knotweed.

Again this year we commissioned leading pollsters YouGov to carry out a survey on Japanese knotweed so we could find out more about people's perceptions of this most troublesome of weeds. If allowed to grow, it can lead to serious structural damage, above and below ground, as well as potential legal difficulties and steep devaluations of properties. If you suspect you may have it on your property, it's imperative to take swift remedial action.

YouGov surveyed a sample of the British public and, using a variety of methods, asked if they could identify Japanese knotweed. Most — four out of five people, or 81% — could not, mistaking the weed for something else. Just 19% — less than one-fifth of respondents — were able to spot the weed. This is surprising, given the scale of the Japanese knotweed problem around Britain today and the Environment Agency saying it is “indisputably the UK’s most aggressive, destructive and invasive plant.”

Plants Mistaken For Japanese Knotweed

Those who took part in the YouGov survey were shown five photographs of Japanese knotweed and asked if they knew what the plant was. The weed was incorrectly identified a number of plants, as follows, including descriptions from gardening authorities:

Bindweed (14% of respondents)
Hedge bindweed or bellbind (Calystegia sepium) with its pure white trumpet flowers is a familiar sight, choking plants in borders and twining around any plant shoot or cane. The smaller field bindweed (Convolvulus arvensis) with white or pink flowers is problematic in long grass and bare soil.
Houttuynia are rhizomatous perennials with pungently orange-scented, heart-shaped leaves and tiny yellow flowers in spikes with usually four prominent white bracts at the base. H. cordata is a wide-spreading herbaceous perennial to 30cm in height, with dull blue-green leaves and dense flower spikes in late spring
Also known as Polygonum baldshuanicum, this has long wiry stems sparsely clad with smallish leaves. The flowers are long airy sprays of creamy white bracts that almost cover the plants from midsummer to autumn. Plants grow at a tremendous rate, and can put on over 4m (13ft) in a year, which makes them ideal for covering eyesores like outbuildings, or screen walls, quickly. Grow them up frameworks of posts and netting or along chain link fencing for a fast boundary 'hedge' that needs little clipping. The Royal Horticultural Society has given it its Award of Garden Merit.
Ivy (6%)
H. helix is a vigorous, self-clinging climber with three- to five-lobed, glossy, evergreen leaves, often with pale green veins, and some reddish or bronzy colours in autumn. Mature plants produce bushy, non-clinging branches with diamond-shaped leaves, and small, nectar-rich, greenish-yellow flowers in clusters of rounded heads in autumn, followed by black berries in winter.

Removing Japanese Knotweed from an Infested Location

Japanese knotweed is most identifiable, meanwhile, by its heart-shaped leaves, rapid growth and off-white flowers that appear in the late summer. Dealing with it is a matter of urgency, and one for professional Japanese knotweed eradication firms to undertake, as DIY efforts almost always fail — leaving you out of pocket and with loads of wasted time and effort.

It means using a powerful herbicide over a number of growing seasons, or carrying out a dig-out at the site of a Japanese knotweed infestation. The latter is suitable in circumstances where quick eradication is necessary, perhaps for a property sale or development. And both will ensure that the problematic roots are either killed off or removed so that the plant doesn’t start growing and causing trouble all over again.

Leading Japanese knotweed removal firms will also be able to provide an insurance-backed guarantee of up to 10 years, so you have total peace of mind.

If you suspect you may have troublesome Japanese knotweed on your property, but are having problems identifying it, Environet is here to help. Just send us some photos to expert@environet.com and we'll tell you what it is, for free. You can also call us, on 01932 868 700.

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