Japanese knotweed (Fallopia japonica) is an invasive plant species that can be found in most parts of the UK. The plant has several identifying features; some of the most prominent features for identifying Japanese knotweed include:
- Large, heart-shaped leaves
- Clusters of small white flowers
- Bamboo-like stems
How to identify Japanese knotweedTo identify Japanese knotweed accurately, you’ll need to know exactly what it looks like. To help you out, we’ve put together a nifty Japanese knotweed identification guide to help you determine whether the suspicious new plant on your property is Japanese knotweed or something less menacing.
Have a click around our Japanese knotweed visual guide to see its key characteristics:
Japanese knotweed identification guide:When it comes to Japanese knotweed identification, there are a few features you can keep an eye out for. These are the most distinctive features that can be used to identify knotweed:
When Japanese knotweed’s leaves first emerge in the spring, they are a bold burgundy colour and are rolled up around the tip of the knotweed shoot, looking similar in shape to an asparagus! As the season draws on and we get closer to summer, the leaves begin to unfurl to display a deep green colour and red veins. A fully-grown Japanese knotweed leaf is the green heart shaped leaf that is typically associated with knotweed.
If you identify Japanese knotweed leaves appearing in your garden, we recommend enlisting the help of a Japanese knotweed specialist as soon as possible.
Japanese knotweed stems are dense, hollow, and wood-like in texture. Because of this, they are often mistaken for bamboo! In the springtime when the knotweed shoots are young and small, the shoots are not hollow; they’re very thin, malleable, and grow in an iconic zig-zag pattern.
Like many plants, Japanese knotweed grows flowers during the summer months. The flowers themselves can be identified by their off-white colouring and by how they grow in small clusters. The flowers themselves are rather pretty – it’s a shame about the rest of the plant!
The rhizome (or root) of the Japanese knotweed plant is the underground invader that allows Japanese knotweed to spread as far and as fast as it does. You can identify knotweed roots by the bright orange shade on the inside and the darker brown colour on the outside.
Identifying Japanese knotweed throughout the yearJapanese Knotweed looks very different during the different phases of its life. The best time of year to identify knotweed is in the mid-to-late summer, when the plant is fully grown and its distinctive leaves and flowers are on full display. We’ve put together a handy pocket-guide to help you identify Japanese knotweed all year round.
SpringDuring the spring, Japanese knotweed begins to regrow after dying down for the winter. Typically starting in mid-March, red and purple shoots will begin to push through the soil and quickly begin growing leaves. These leaves will begin life tightly curled up to the stem in a purplish colour, and begin to unfurl as summer draws closer.
SummerIn the height of the summer, Japanese knotweed is in full swing. Bright and full, it appears green and leafy above ground, with purple-speckled stems. This is when you’ll spot those creamy-white Japanese knotweed flowers. The leaves in summer will be a vibrant green colour with reddish veins, growing anywhere from 10-20cm long.
AutumnAs the lush green of the summer turns to autumnal auburn, Japanese knotweed follows suit. Its leaves will turn a yellowy gold, while the stem will fade to a darker brown.
WinterAs temperatures drop, the wintertime design of Japanese knotweed becomes far less colourful. Brown and bare, the weed retreats back to its rooty rhizomes, leaving behind its woody stalks. All flowers and leaves will completely die away, being no longer visible until spring rolls around again.
Knotweed or not? That is the question...Thankfully, not all suspected cases of Japanese knotweed are the real deal. In fact, the villainous vine has many doppelgangers and most instances of suspected knotweed are merely a case of mistaken identity.
Before you start panicking or butchering your back garden, be sure you have a genuine case of Japanese knotweed on your hands. Many plants look like Japanese knotweed, including the following species:
Baring heart-shaped leaves like its Japanese twin, this also has a rapid growth spurt when it first appears in the springtime.
However, unlike Japanese knotweed, Bindweed isn’t capable of supporting itself and, instead, makes its vertical ascent by coiling itself around the stems of other standing plants.
It also boasts large flowers in the summertime, clearly differentiating itself from traditional Japanese knotweed.
Much like Japanese knotweed, Russian Vine has similar looking leaves and flowers, while it is also fast-growing.
On the other hand, it is also similar to Bindweed in that it relies on other plants to grow upward, twisting and climbing around the stems of taller, more solid vegetation.
The most widely known of its contemporaries, bamboo grows tall like knotweed and also has visible nodes on its stem, making the two very similar in appearance.
That being said, bamboo stems are considerably denser than its Asian brethren and boast a strong sturdiness lacking in Japanese knotweed. Bamboo leaves are also notably narrower and longer.
Part of the same family, Broadleaf Dock shares numerous characteristics with Japanese knotweed, from its arrangement of leaves to the spiky shape of its flowers and stems.
However, this plant is typically shorter than Japanese knotweed and contains a foamy substance in its stem, clearly visible when cracked open.
What to do if you identify Japanese knotweedIf you identify Japanese knotweed growing on (or near) your property, you should call a specialist ASAP. Someone who’s used to dealing with Japanese knotweed on a regular basis will be able to confirm the plant’s identity, determine the severity, and advise you on the best course of action.
Get in touch with the Taylor Total Weed Control team if you'd like us to perform a free, discreet, no-obligation survey of your suspect shrub.
We offer a range of Japanese knotweed treatment plans, as well as a Japanese knotweed insurance-backed guarantee for added reassurance.