Japanese Knotweed causes havoc on gardens and structures. Despite being an attractive plant, it must be destroyed at all costs. Make sure you’re killing the real Japanese Knotweed, and not an innocent plant that looks similar.
There are 10 plants that look like Japanese Knotweed. They are Bindweed, Houttuynia, Lilac, Russian Vine, Broadleafed Dock, Honeysuckle, Bamboo, Himalayan Honeysuckle, Horsetail, Himalayan Balsam and Buckwheat.
A Japanese knotweed infestation on your property can be highly damaging. It can be costly to remove, too. Many plants look like Japanese Knotweed, making its identification challenging. Before you rip out most of your garden in a panic, stop, think and make sure you know how to identify the real Japanese Knotweed
What is Japanese Knotweed?
Japanese Knotweed is a perennial weed. Unfortunately, it is one of the most highly invasive plants globally and capable of causing lethal damage to your garden, grounds and property.
Japanese Knotweed can overpower your beautiful landscape. It can also crawl through your building’s foundation and onto your neighbor’s property or vice versa. Once it takes hold, it can and will create horrible havoc there, leaving both you and your neighbour devastated!
Having Japanese Knotweed on your property is bad news and has been known to bring down the value of your property. Even mortgage lenders will turn you down when they find out Japanese Knotweed can be found on the property or in its surrounding area.
• It is a highly invasive and rapidly spreading ornamental weed that passes for a harmless plant.
• It can grow fast and reach heights of as much as 10 feet.
• Its rampant growth can cause its rhizomes to sprout through cement cracks, rock walls, asphalt, and flashboards.
• It can grow a distance of as far as 70 feet from its stem.
• It has roots that can imbed twice as deep.
• It can be so dense that it can block all sunlight other plants need to grow.
• It can cause devastating structural damage to your home.
• It is difficult to remove.
• It looks innocent and harmless and fairly pretty.
This means removal and control of Japanese Knotweed is a laborious and problematic task.
What Does Japanese Knotweed Look Like?
It can be challenging to identify Japanese Knotweed. During mid-summer and autumn are the best times to identify Japanese Knotweed.
The roots/ rhizomes of Japanese Knotweed spread underground. The plant flowers in late summer, and it dormant yet alive during the winter. Then it appears again the following spring.
Japanese Knotweed is often mistaken for common shrubs. However, it can be identified by its characteristics which include:
• Flowers – Creamy white color. They are 0.5 cm. wide and form clustered panicles (loose branch of clusters of flowers). Its panicles can grow to 10cm. The flowers bloom in late summer (August or September).
• Leaves – Light green with purple or red flecks. They are shovel or heart-shaped and have pointed tips. The leaves shoot out from nodes typically in an alternate zigzag pattern.
• Roots – The roots are about 20 cm in diameter. Inside roots are yellow/orange and outside roots are dark brown. The roots (rhizomes) can grow between 3 to 7 meters horizontally and 3 meters deep.
• Stems – The stems are green with red and purple speckles. They are hallowed and grow to 2-3 meters in height and in a zigzag pattern. There are visible nodes between the stems.
• Height – Can grow from 7 feet to 9 feet.
New Japanese Knotweed grows from pieces of green stem or nodes in water or soil. They belong to the Order Caryophyllales and the Reynoutria japonica (the Polygonaceae family) and are natives of China, Japan, and certain parts of Taiwan and Korea.
Plants that Look Like Japanese Knotweed
Although the Japanese Knotweed has its unique features, it takes a keen eye and some knowledge for correct identification. It is often confused with many other plants; thus, isolating an infestation can be difficult.
The presence of Japanese Knotweed always creates hysteria because of the severe damage it can create to your property. It, therefore, comes as no surprise that many property owners get paranoid when they find what they think is Japanese Knotweed.
With the numerous horror stories about the costly consequences and destruction caused by Japanese Knotweed, remember that there are other plants that are less harmful. The problem is some of these are plants that look like Japanese Knotweed.
If you suspect there is Japanese Knotweed on your property, carefully inspect the plant so that you don’t mistake it for an innocent plant.
Here are the similarities and differences of each of these plants often mistaken as Japanese Knotweed:
Similarities between Bindweed and Japanese Knotweed
• Bindweed has the same heart-shaped leaves as Japanese Knotweed.
• It also has the same invasive and aggressive growth.
• Just like Japanese Knotweed, bindweed sprouts in early spring.
• It can also rapidly cover a large amount of space.
Differences between Bindweed and Japanese Knotweed
• Japanese knotweed is stronger than bindweed.
• Bindweed needs to bind itself around plants, while Japanese Knotweed grows on top and does not entwine with other plants.
• Bindweed has heart-shaped leaves with lobes on both sides of the stalk. Japanese Knotweed also has heart-shaped leaves but no lobes on their stalks.
Similarities between Houttuynia and Japanese Knotweed
• Houttuynia is also a perennial plant that comes with heart-shaped leaves similar to Japanese Knotweed.
Differences between Houttuynia and Japanese Knotweed
• It is only one-tenth the size of Japanese Knotweed.
• It has small white flowers, while Japanese Knotweed has creamy white flowers.
• It can grow to only around 30 cm high.
Similarities between Lilac and Japanese Knotweed
• It also has spade-shaped and green leaves.
Differences between between Lilac and Japanese Knotweed
• It has woody stems, while Japanese Knotweed has hollow stems.
• It is not too invasive compared to Japanese Knotweed.
4. Russian Vine
Similarities between Russian Vine and Japanese Knotweed
• Russian vine comes from the same genus as Japanese Knotweed.
• It also has similar spade-shaped leaves as Japanese Knotweed.
• Russian vine also has a rapid growth.
Differences between Russian Vine and Japanese Knotweed
• It needs to entwine itself around another plant or something solid, while Japanese Knotweed does not display this behavior.
5. Broad Leafed Dock
Similarities between Broad Leafed Dock and Japanese Knotweed
• Its new leaves unfurl in the same manner as Japanese Knotweed.
• It has similar leaf arrangements.
• Flowers and stems have the same spiky shape as Japanese Knotweed.
Differences between Broad Leafed Dock and Japanese Knotweed
• Broad leafed dock grows to only one meter tall.
• Its stem has a clear and visible foamy substance when cracked open.
Similarities between Bambooand Japanese Knotweed
• Bamboo has similar stems with clear nodes as Japanese Knotweed.
• Bamboo can grow as tall as Japanese Knotweed.
• Similar to Japanese Knotweed, Bamboo grows new shoots from creeping rhizomes.
• Bamboo has rapid growth, too. They are the fastest-growing plant in the world.
• Bamboo is also invasive and quickly spreads in unwanted areas.
• Bamboo and Japanese Knotweed are challenging to get rid of with herbicides.
Differences between Bamboo and Japanese Knotweed
• Bamboo leaves are long and slender.
• Bamboo stems are extremely hard and cannot break as easily as Japanese Knotweed.
7. Himalayan Honeysuckle
Similarities between Himalayan Honeysuckle and Japanese Knotweed
• Stems are also hollowed and look a lot similar to Japanese Knotweed.
• Stems are also hollow and can easily snap.
• It is also an invasive plant.
Differences between Himalayan Honeysuckle and Japanese Knotweed
• Himalayan Honeysuckle has drooping white flowers with red-purple bracts.
• Leaves grow in pairs, while Japanese knotweed leaves grow individually and alternately along the stems.
• Stems are pale green and do not have purple speckles.
• Himalayan Honeysuckle leaves are arranged alternately along the stems.
Similarities between Horsetail and Japanese Knotweed
• Strobili (spore-bearing bodies) sprout through the ground in spring rapidly, making them seem quite invasive. People sometimes think they are young Japanese Knotweed plants.
• Green leaves and stems are segmented into nodes quite similar to Japanese Knotweed.
Differences between Horsetail and Japanese Knotweed
• Sprouting green leaves and shoots quickly replace dead strobila.
9. Himalayan Balsam
Similarities between Himalayan Balsam and Japanese Knotweed
• Stems of Himalayan balsam and Japanese Knotweed are hollowed.
• Himalayan balsam can grow up to 2.5 meters, the same height as some mature Japanese knotweed.
• Himalayan balsam can also cover large areas and are highly invasive.
Differences between Himalayan Balsam and Japanese Knotweed
• Flowers of Himalayan balsam are pink, prominent, lipped, and hooded.
• Flowers start to form in mid-summer to late summer.
• Leaves are thinner and longer than those of Japanese Knotweed.
• Leaves are arranged alternately along each stem.
Similarities between Buckwheat and Japanese Knotweed
• Buckwheat and Japanese Knotweed belong to the same family (Polygonaceae).
• They look similar, especially when flowerless.
• Stems come with mark nodes.
• Leaves along the stems are arranged alternately.
Differences between Buckwheat and Japanese Knotweed
• Flowers of Buckwheat are much shorter yet larger than Japanese Knotweed.
• Buckwheat flowers are clustered at the ends of stems and vary in color from white to pink.
• Leaves are thin, long, and triangular.
• Leaf base tends to clasp around the stems.
• Buckwheat is shorter than Japanese Knotweed (0.6 meter).
• Buckwheat has a sheath in stems while Japanese Knotweed does not.
While these plants do not have precisely similar features as Japanese Knotweed, they have enough similarities to make you anxious there is an infestation.
How to Deal with Japanese Knotweed
To effectively deal with Japanese Knotweed, you should first be able to identify them.
The earlier an infestation is detected, the more likely dealing with them will be successful. It will also cost less effort, time, and resources.
• Cut the stems as closest to the ground as you can get.
• Carefully dispose of cut stems.
• Avoid placing Japanese Knotweed in a compost pile because they can contaminate the soil and start to sprout and spread.
• Cover the area where you cut the stems with a dark material weighed down by heavy bricks, rocks, etc., for an entire growing season.
• Excavate Japanese Knotweed using heavy machinery to dig the plants and their roots from the ground.
Controlling Japanese Knotweed should not be done only on your property. Japanese Knotweed has a highly invasive and extensive root system; thus, you should alert your neighbors and see if they also have Japanese Knotweed on their property.
You do not have to deal with Japanese knotweed infestation yourself. There are Japanese knotweed removal services that can do their job.
Japanese Knotweed Infestation
Japanese Knotweed spreads rapidly during the summer. It can easily cross borders and spread to your property. More often, a garden fence offers little defense to a possible invasion from the garden of your neighbor.
Remember that Japanese Knotweed in your neighbor’s property can affect the value of your property because an infestation can reach your property.
The amount your property will devalue because of having a Japanese knotweed infestation next door depends on the severity of the infestation and how close it is to your property. Japanese Knotweed infestation within about 7 meters of your property will devalue your property.
Japanese Knotweed always spells trouble. It reduces the value of your home and causes havoc on buildings.
The problem is, this terrible enemy of gardens and buildings is a beautiful looking plant and, obviously, great for pollinators.
Thoroughly study the above list of plants that resemble Japanese Knotweed. If you are still not sure of what you have on your property, you should ask for the assistance of the experts.
Our gardens are our pride and joy. We defend them vigorously – and rightly so. Just make sure you’re destroying enemies and not friends, and your garden will continue to thrive and flourish under your tender and protective care!