Japanese knotweed growing on open ground

What does Japanese knotweed look like?

Here we show images of knotweed plants, its leaves, flowers, stems, shoots, roots and crown, what it looks like through the seasons, some ‘lookalikes’ and pictures of knotweed damage.

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IDENTIFICATION TOOL

Japanese knotweed in pictures

Knotweed changes through the seasons. If left to its own devices it will form a dense canopy of foliage like the picture above, blocking out sunlight and depleting oxygen for the flora or fauna trying to survive underneath. But what are the individual characteristics of knotweed that define this species from other (many) lookalikes? And getting the identification wrong can lead to serious issues. So, for anyone who wants (or needs) to identify this highly invasive species knowing what the plant, leaf shape, spines, flowers, roots and shoots look like is essential, this ‘at a glance’ page is packed with pictures to help.

What do Japanese knotweed plants look like?

Japanese knotweed has shovel shaped leaves that start off looking like this as early growth.

Japanese knotweed first emerges as small shoots that can be easily missed.

The clear zig-zag leaf growth pattern is it's most defining characteristic. — The clear zig-zag leaf growth pattern is it’s most defining characteristic.

Japanese knotweed plant in full growth forms dense bushes (or stands) that can reach 3.5 metres high.

What do plants that look similar to japanese knotweed look like?

Russian vine has similar flowers to Japanese knotweed but the leaves are not shovel-shaped and smaller.

Himalayan Honeysuckle has similar shaped leaves to Japanese knotweed but look cloesly and you'll notice they are more pointed at the tips. The flowers are also pinky-purple, unlike Japanese knotweeed's creamy-white flowers. — Himalayan Honeysuckle has similar shaped leaves to Japanese knotweed but look cloesly and you’ll notice they are more pointed at the tips. The flowers are also pinky-purple, unlike Japanese knotweeed’s creamy-white flowers.

Dogwood leaves look similar but the growth pattern does not match Japanese knotweed, zig-zag pattern. Certain Dogwood varieties have red stems which can appear similar to Japanese knotweed.

Bindweed has similar shaped leaves but the growth patter is completely different to Japanese knotweed and the flowers, though white are much larger than the small clusters that grow on knotweed.

what does japanese knotweed look like through the seasons?

Japanese knotweed in spring with asparagus like tips

Japanese knotweed in summer with bright green foliage on tall stems

Japanese knotweed in autumn with golden coloured leaves

Japanese knotweed in winter has brown brittle canes

What do Japanese knotweed leaves look like?

Japanese knotweed leaves grow in a horizontal pattern from each stalk, one on each side in a zig-zag pattern — Japanese knotweed leaves grow in a horizontal pattern from each stalk, one on each side. The stalk grows in a zig-zag shape with one leaf from each zig and zag. Leaves are ‘shovel’ shaped and can be larger than your hand.

Japanese knotweed leaves in summer are bright green with red stems where they join the main branch.

Young Japanese knotweed leaves appear as darker green leaved that are curled up at first then uncurl.

Japanese knotweed leaves in autumn turn golden with red speckles.

What do Japanese knotweed shoots look like?

Young shoots appear much like asparagus but with red tips.

As the Japanese knotweed shoots grow the green stems emerge with leaves about to unfurl. — As the shoots grow the green stems emerge with leaves about to unfurl.

The Japanese knotweed leaves start to appear once the shoots have fully emerged from the ground. — The leaves start to appear once the shoots have fully emerged from the ground.

Young shoots growing from the underground crown among the previous year's dead canes. — Young shoots growing from the underground crown among the previous year’s dead canes.

What do Japanese knotweed flowers look like?

Japanese knotweed flowers are small creamy white and form clusters along thin stems.

Close up of Japanese knotweed flowers in summer show single flowers growing from a central stem.

Japanese knotweed flowers are prolific and grow in clusters along the stems.

A close up of Japanese knotweed flowers growing along stems.

What do Japanese knotweed stems look like?

A close up view of the distinctive patterning on the stems in summer.

Close up of hand holding a Japanese knotweed stem. — Japanese knotweed stem and leaf shoot emerging from it. In the background you can see last year’s canes.

Japanese knotweed stems showing it's fleshy inside and hollow centre. — Japanese knotweed stems showing it’s fleshy inside and hollow centre.

Close up of Japanese knotweed brittle woody stem in winter. — Japanese knotweed stem in winter is brittle and woody – called a cane at this stage.

What do Japanese knotweed roots (rhizomes) look like?

Inside of a Japanese knotweed rhizome showing its orange coloured flesh. — Japanese knotweed roots are called rhizomes. They form an underground root system that shoots to form new plants above ground. If disturbed fragments of root as small as your thumbnail will generate a new plant.

Broken Japanese knotweed rhizome showing inside its orange colouring. — The rhizomes are defined by their bright orange colouring inside.

Close up of Japanese knotweed rhizomes showing fibrous outer texture — Rhizomes have a fibrous outer texture that is visible when cleared of mud debris.

Japanese knotweed rhizomes showing branches and tendrils of new growth. — Rhizomes showing branches and tendrils of new growth.

What do Japanese knotweed crowns look like?

Close up of a Japanese knotweed crown. — The Japanese knotweed crown is the main ball from which new plants profligate. Crowns can be the size of your hand or much larger, with multiple shoots growing from them.

A large Japanese knotweed crown with most of it being visible above ground. — An example of a large Japanese knotweed crown with most of it being visible above ground.

A Japanese knotweed crown with new growth visible, and surrounded by last year's canes. — A Japanese knotweed crown with new growth visible, and surrounded by last year’s canes.

Japanese knotweed crown growing alongside (and underneath) a brick wall. — Japanese knotweed crown growing alongside (and underneath) a brick wall. This is what an encroaching plant looks like as the underground rhizomes have clearly spread onto another property.

What does Japanese knotweed encroachment look like?

Japanese knotweed growing over a neighbour's fence. — Japanese knotweed growing over a neighbour’s fence. Whilst the knotweed is not (yet) growing in the neighbour’s land it is restricting their amenity use and the neighbour could take legal action.

Japanese knotweed encroaching through a gate onto a neighbour's land. — Another example of Japanese knotweed encroaching through a gate onto a neighbour’s land. In this case the knotweed rhizomes will easily spread forming new plants where they are not wanted. Again legal action could be taken by the neighbouring land owner if the knotweed is not managed under a Knotweed Management Plan, or completely removed via excavation.

Japanese knotweed growing underneath a fence. — This is how knotweed spreads from property to property. Because it grows underground via its rhizome system it can very easily pop up next door!

Japanese knotweed growing alongside a railway line. — An example of Japanese knotweed out of control on land owned by a rail company. This will not only be a problem for the company, but for any residential or commercial land owners or homeowners that this land backs onto.

What do Japanese knotweed problems look like?

Japanese knotweed will exploit weak areas such as cracks or gaps in structure, and will grow through them, as seen here growing though a crack in concrete.

Japanese knotweed bonsai growth - this much smaller (mini-version) of the plant can appear after year one of treatment. — Japanese knotweed bonsai growth – this much smaller (mini-version) of the plant can appear after year one of treatment. As the herbicide takes effect the leaf growth is much less, and eventually will be exhausted by the herbicide and go into a dormant state.

Man wading through a swathe of Japanese knotweed undergrowth. — Japanese knotweed undergrowth – this is how knotweed will grow if left uncontrolled – it will out-compete native plants by depleting sunlight and oxygen to anything trying to survive underneath its dense canopy.

Japanese knotweed overgrowth on a residential property. — Japanese knotweed will quickly smother land if left uncontrolled, wiping out other plants and altering the ecosystem it’s invading. Many species of flora and fauna will struggle to exist in this altered habitat.

What does Japanese knotweed damage look like?

Japanese knotweed growing internally through a crack in the skirting board of a house.

Japanese knotweed growing through gaps in a brick wall.

Japanese knotweed growing through the bonnet of a car.

Japanese knotweed growing through cracks in concrete.

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