• The leaf shape of many woody shrubs and small/young trees can look very similar to knotweed (e.g. lilac, dogwood and poplar).

• Knotweed stems are not at all woody, so anything with bark that can be stripped or twigs that snap to show a solid, woody core are not knotweed.
• Dogwood and lilac are often confused with knotweed due to their similar leaf shapes. However, these species have leaves that grow opposite each other along their woody stems.

• Shoots and leaves are very similar to young knotweed shoots. So much so that around 1825, when Japanese knotweed was first introduced to the UK by the Horticultural Society of London at their Chiswick garden, the plant was erroneously thought to be Houttuynia cordata.

• Plants only grow to 30cm or so in height.
• Flowers are produced in spring and appear to have four to six, large, white, petals (they are actually flower bracts at the base of the yellowish flower spikes).

• Ornamental bistorts are commonly planted decorative garden species. They are closely related to Japanese knotweed and are in the same genus as Himalayan knotweed (Persicaria wallichii).
• Red bistort is probably the most common. It and many other ornamental bistorts have leaves and stems that are very similar to knotweed species, and when not in flower they can easily be mistaken for them.
• Stems are hollow and separated into nodes like knotweed.
• Leaves are alternately arranged along stems, like knotweed.

• Ornamental bistorts are usually planted on purpose and don’t spread widely. Therefore, they are usually located in planted borders and areas of landscaping.
• Flowers appear in summer and early autumn and are very different to those of Japanese knotweed. They form small clusters of pale pink/white to bright red/purple ‘lollipops’ on tall (10cm) straight ‘sticks’.
• Leaves are longer than those of Japanese knotweed, appearing more like those of Himalayan knotweed, with marked lobes that overlap slightly around the stems.
• Bistorts have very long, semi-translucent, leaf sheaths (fused stipules) that envelop the stem nodes (bamboo-like rings from where leaves sprout) for almost the entire length of the stem internodes (the smooth, straight bits of stem between the nodes). These sheaths are absent on Japanese knotweed and are generally shorter on Himalayan knotweed.
• Stems are much thinner and shorter than knotweed, generally growing to around 1m tall and less than 1cm in diameter.
• Some varieties and species of ornamental bistort have dark, triangular, arrow-shaped blotches across the central midribs of the leaves.

• Lesser knotweed is another relatively common ornamental Persicaria species that is closely related to Himalayan knotweed (Persicaria wallichii). As such it is often mistaken for this species or for Japanese knotweed.
• As with other knotweed species, lesser knotweed has the same, bamboo-like, hollow stems with alternately arranged leaves.

• Leaves are long, thin and ovate (i.e. an elongated ellipse-shape) with clearly marked parallel veins, unlike Japanese knotweed.
• Lesser knotweed is shorter than Japanese knotweed, growing approximately 1.5m tall.
• Individual flowers are much bigger than those of Japanese knotweed and are clearly bell-shaped. They range in colour from pale to bright pink.

You can read all about this invasive non-native weed on our Himalayan balsam page. It contains details on: why it’s a problem; how to identify it; and how to control it. There are also links to other sources of useful guidance.

• Himalayan balsam is the tallest annual plant in the UK, growing up to 2.5m; thus reaching the same height as some mature knotweed.
• Stems are hollow.
• Plants are very invasive and can cover large areas – particularly close to watercourses.

• Leaves are arranged opposite each other along stems.
• Leaves are longer and thinner than those of knotweed and have a pale pink midrib (which can make them look a bit like Himalayan knotweed – Persicaria wallichii).
• Flowers form in mid to late summer and are large, pink, hooded and lipped.
• Seed pods follow shortly after flowers and once mature are explosive when touched (this is the plant’s mechanism for seed dispersal over several metres).

• Docks are in the same family as knotweed (Polygonaceae) so it’s not surprising they share several similar features.
• Leaves are arranged alternately along stems.
• Flowers and seeds form in spikes that look similar to knotweed.
• In winter, when the leaves and stems die back, the persistent stems of dock, with their old seed bracts, can look very similar to dead knotweed stems and seed bracts.

• Stems are fluted and are shorter than knotweed plants, growing up to 1m tall.
• Stems are not completely hollow, containing a foam-like pith.
• Leaves form rosettes close to the ground at the base of the stems and are much larger than those of knotweed (up to 1m long).

• Heart-shaped leaves can look similar to knotweed.
• Leaves are arranged alternately along stems.
• Plants are invasive and can very quickly appear in early spring, covering wide areas.

• Bindweed shoots do not stand up by themselves. It is a climbing plant that grows by twisting around the erect stems of other plants.
• Flowers appear from early summer as large, pink or white, trumpets.

• Bamboo stems have clear nodes like knotweed and can grow as tall, or taller.
• Plants can be invasive and easily spread to areas where they are not wanted. They can also be very difficult to effectively treat with herbicides.
• Growth of new shoots are from creeping rhizomes and can be extremely rapid (bamboos are the fastest growing plants in the world!).

• Stems are very hard and cannot be snapped easily like knotweed.
• Leaves are very slender and long (varies between species and varieties, but usually up to 50cm).

• Stems are bamboo-like and can look a lot like knotweed. They are also mostly hollow and can be snapped relatively easily.

• Leaves are arranged opposite each other along the stems.
• Stems are pale green with no purple speckles.
• Flowers appear in summer and autumn and are very distinct, forming drooping, pendulous racemes of white flowers, with showy red-purple bracts. Deep purple berries later form along the racemes, between the red-purple bracts.

• Russian vine (or Bukhara fleeceflower) is in the same genus (Fallopia) as knotweed (although it is a separate genus if knotweed is considered to be within the genus Reynoutria). As such, pollen from Russian vine commonly pollinates the female flowers of Japanese knotweed. However, the resulting seed almost never produces viable plants (which would be Fallopia x conollyana, or x Reyllopia conollyana – the “x” denoting an interspecific or intergeneric hybrid, respectively).
• Being closely related, the leaves and flowers of Russian vine appear quite similar to those of knotweed.
• It is incredibly fast growing and invasive – its common name is ‘mile-a-minute’!

• Russian vine is a climbing plant that relies on the erect stems of other plants or solid structures to twist around and grow upon. As such, it is very commonly used as a screening plant or to quickly provide cover over fences and other structures.

• The spore bearing bodies (strobili) appear in spring, sprouting through the ground at a sometimes alarming rate making them appear quite invasive. This can sometimes worry people into believing they could be young Japanese knotweed shoots.
• Following the strobili, which die back once they’ve released their spores, the green stems and leaves quickly emerge in a similar fashion. These are segmented into nodes, a bit like Japanese knotweed, so they could potentially be mistaken for young knotweed shoots.

• Once the strobili have died back they are rapidly replaced by sprouting green shoots and leaves that quickly develop into the brush-like growth that gives horsetail its name. These are very distinctive and do not at all resemble mature Japanese knotweed plants.

• Buckwheat is in the same family as knotweed (Polygonaceae) and as such it can look quite similar, particularly when shoots are young and flowerless.
• Leaves are arranged alternately along the stems.
• Stems have marked nodes, like bamboo.

• Plants are much shorter, growing to a height of approximately 0.6m – they often appear in odd places from spilled bird seed or from cheap wildflower seed mixes.
• Flowers are much larger, varying in colour from white to pink, and appear in clusters on the ends of stems.
• Leaves range from triangular to a long, thin, pentangular shape, with the leaf bases sometimes clasping around the stems.
• The dried seeds are much larger than those of Japanese knotweed and produce a pseudo-cereal grain that is an important food crop in some countries, being used to make soba noodles, blini pancakes and a porridge called kasha

• It can be quite invasive and difficult to get rid of
• Fragmenting the roots by digging and disturbing them can quickly spread plants to new areas
• Stems die back in the winter, with new shoots emerging in the spring

• The leaves are very different, being compound (comprising a number of small leaflets and appearing like rose or ash leaves)
• Flowers appear in summer in large umbels, like cow parsley and hogweed
• Flower stalks are much shorter than knotweed stems, being up to approximately 1m tall

• It can appear invasive because it shades other plants and can quickly colonise new areas.

• The leaves are very different, being evergreen (i.e. present in winter) and a range of shapes from roughly triangular to 5-lobed
• Leaves can vary in colour from shiny dark green to variegated forms with white or yellow blotches or streaks
• It grows by climbing over trees shrubs and built structures like walls, using special hairs that grow from its stems
• Its stems are solid and woody

• Being in the same family as Japanese knotweed, it looks very similar, particularly its stems, which are separated into knotweed-like nodes

• The most striking difference is the flowers, which form large plumes of fluffy white flowers from summer to autumn
• Its leaves are longer and thinner, appearing a bit like Himalayan knotweed
• It tends to form bushes, with foliage present to the ground, somewhat hiding the stems, which are not blotched red like Japanese knotweed

• It can grow very fast, seemingly out of control
• Its leaves are arranged alternately along the stems
• The leaves are a similar shape to hybrid knotweed

• The edges of the leaves have many tiny spines on them
• The young stems are furry
• The older stems are woody
• Large white flowers are produced in early summer, which develop into distinctive furry fruits

• Plants can appear quite invasive and will often grow from hard surfaces and built structures like roads, pavements and walls
• It commonly appears along railways and on wasteland
• Leaves are arranged alternately along the stems

• The old stems are solid and woody
• Flowers are bright purple (sometimes white) forming large distinctive spikes in mid-summer
• The undersides of the leaves are much paler than the upper sides

• The leaf shape can look quite similar to knotweed
• Some varieties have red stems, which can make them appear similar to knotweed
• In winter, the leafless stems can look similar to knotweed canes

• Leaves are arranged opposite each other along the stems
• There are conspicuous parallel veins on the upper sides of the leaves
• Stems are woody

• The leaf shape can look quite similar to hybrid knotweed

• Leaves are arranged opposite each other along the stems
• The stems are woody
• Large spikes of flowers are produced in early spring, which can be a wide range of colours, including white, blue or purple

• It can quickly colonise new areas, and out compete other plants, making it quite invasive
• When the stems die back in winter, the remaining ‘crowns’ can appear similar to knotweed, with the broken or cut stem scars appearing hollow, a bit like knotweed canes
• It often grows readily through small cracks in concrete and brickwork, causing damage to some built structures

• The leaves are arranged opposite each other along the stems, and have no petioles (stalks)
• The flowers form distinctively large clusters that are bright pink/red, appearing early in the summer until autumn
• Mature plants are much shorter, usually being less than 1m tall