6 Plants That Look Like Japanese Knotweed

Gardening takes a lot of care and attention, like raising a child going through school. Plant bullies are similar to real ones at schools in that they hinder, prevent, and spoil the growth of your other plants!

Japanese knotweed, in particular, is problematic because It can outcompete native plants, leading to a decrease in biodiversity and a loss of habitat for native wildlife. The plant’s robust root system and rapid growth can cause damage to buildings, roads, and other infrastructure.

Not everyone is an experienced botanist, so how do you differentiate plants that look like Japanese knotweed? Let’s look at the most common examples; by the end, your garden will thank you for it!

1. Houttuynia (Houttuynia Cordata)

Houttuynia Cordata
Andrey Zharkikh Houttuynia Cordata

Houttuynia cordata and Japanese knotweed (Fallopia japonica) have striking differences despite similar appearances. Houttuynia cordata is a herbaceous perennial plant native to China and Japan, while Japanese knotweed is an invasive plant species native to East Asia.

Houttuynia cordata is a low-growing plant with heart-shaped leaves and small, white or pink flowers. It is often used to cover the ground or in herbal medicine. They grow to about 11.8 inches (30 cm) and appear much earlier in the season.

You can expect to see them with four to five petals with a yellow spike in the center of the flower.

On the other hand, Japanese knotweed is a tall, herbaceous perennial plant with bamboo-like stems and large, heart-shaped leaves. It can grow up to 10-13 feet (3-4 m) in height and also has small, white, or pink flowers.

It is an invasive species in many parts of the world because it can outcompete native plant species and cause damage to infrastructure.

You can distinguish Houttuynia cordata and Japanese knotweed by visual similarities like their heart-shaped leaves and a flat base (the part of the leaf closest to the stem).

The leaves are large at 2 – 5 inches (5 – 3 cm), and if you look carefully at the stem, you’ll notice the leaves alternate up the stem.

2. Broad-Leaved Dock (Rumex Obtusifolius)

Broad leaved Dock Rumex obtusifolius
Hornbeam Arts Broad leaved Dock (Rumex obtusifolius)

Rumex obtusifolius, also known as a broad-leaved dock or bitter dock, is a perennial plant in the buckwheat family. It is native to Europe and Asia and commonly found in grassland, meadows, and roadsides.

The plant has a tall, upright stem with large, oblong leaves that are green on the top and reddish-brown on the underside. Their heart-shaped bases look similar to Japanese knotweed; the leaves can grow to 12 inches (30cm) long and 5.9 inches (15 cm) wide.

Broad-leaved dock plants have varying heights of between 1.3 – 4.9 feet (0.4 – 1.5 m), and they produce small green flowers in clusters and seeds in a papery brownish-black seedpod.

Japanese knotweed (Fallopia japonica), on the other hand, is a larger plant characterized by its dense clusters of bamboo-like stems that can grow up to 10 feet tall. The leaves are heart-shaped and have a glossy green appearance.

While both Rumex obtusifolius and Japanese knotweed are herbaceous plants with large leaves and upright stems, they are distinct species distinguishable by physical characteristics such as the shape and color of their leaves, flowers, and seedpods.

3. Dogwood (Cornus Sanguinea)

Cornus Sanguinea
Andreas Rockstein Cornus Sanguinea

Cornus sanguinea, also known as dogwood or bloody-twig dogwood, is a deciduous shrub native to Europe and Asia.

It has slender, red, or purplish-red stems and small green leaves that turn shades of red, orange, and yellow in the fall. The plant produces small, white flowers during the spring season, producing small, blue-black berries.

While Cornus sanguinea and Japanese knotweed may have red stems and small, white flowers, they are distinct species with different physical characteristics and native ranges.

Cornus sanguinea is generally smaller and has green leaves, while Japanese knotweed has larger, oval-shaped leaves and is more aggressive and invasive.

Cornus Sanguinea can grow to 7 – 20 feet tall (2 – 6 m), while their leaves are typically 2 – 3 inches long (4 – 8 cm) and 0.8 – 1.6 inches wide (2 – 4 cm).

If you examine them closely, you’ll notice they consist of dark greenish-brown twigs and branches, and the leaves have an oblong shape with slight discoloration at the bottom of the leaf.

Dogwoods are famous for horticulture, and the dense wood of the larger-stemmed species is valuable for everyday items like cutting boards and tool handles. The red seeds from dogwood are also an essential source of sustenance for several varieties of game birds, including quail.

More about Dogwood: Are Dogwood Berries Poisonous? | Pros And Cons Of Dogwood Trees | 6 Trees Similar To Dogwood

4. Bindweed (Calystegia Sepium)

Calystegia Sepium
Kachigarasu PL (busy) Calystegia Sepium

Calystegia sepium, commonly known as wild morning glory or hedge bindweed, is a perennial flowering plant native to North America. It is a climbing, or creeping plant often found growing along fences, walls, and other structures.

The flowers of Calystegia sepium are typically trumpet-shaped and have a pink or white color. They measure 2-3 inches (5-8 cm) in diameter and have five petals fused at the base to form a tube. The flowers are borne on long, slender stems and typically in clusters.

The leaves of Calystegia sepium are heart-shaped and have a glossy, dark green color. They grow on creeping, twining stems reaching up to 7 – 13 feet (2 – 4 m) tall. Bindweed leaves measure 2 – 4 inches long (5 – 10 cm) and 1.2 – 2.8 inches (3 – 7 cm) wide.

Calystegia sepium is a common weed in many parts of the world, and it is known for its ability to spread rapidly and thrive. It is common in gardens, fields, and along roadsides.

Despite its invasive nature, Calystegia sepium is popular with pollinators, and bees, butterflies, and hummingbirds often frequent its flowers.

Remember that hedge bindweed is toxic and has calystegine alkaloids capable of killing an adult. So be careful if you need to handle them!

5. Russian Vine (Fallopia Baldschuanica)

Fallopia Baldschuanica
Andreas Rockstein Fallopia Baldschuanica

Russian Vine is a perennial vine native to central and eastern Europe. It is known for its rapid growth and ability to climb and is helpful as a decorative plant in gardens and landscaping.

It has green, heart-shaped leaves and small white flowers, and its stems have tiny, sticky tendrils that help it climb.

It has hollow stems with distinctive purple-red speckles, and its leaves are green and heart-shaped. The plant produces small white or pink flowers in the summer and is common along riverbanks, roadsides, and disturbed areas.

In comparison, Russian vine has larger leaves and clusters of small, white, or pink flowers, while Japanese knotweed has smaller, creamy white flowers and smaller leaves arranged in a zigzag pattern along the stem.

Russian Vine is a climbing vine, while Japanese knotweed is a herbaceous perennial plant with long, hollow stems. Japanese knotweed is generally taller and more robust than Russian Vine. It has small, greenish-white flowers arranged in clusters along the stem.

The flowers are typically about 3-4 mm in diameter, have four petals, and grow to 33 feet (10 m), while the triangular leaves grow to 4 inches (10 cm).

They have a distinctive, spicy fragrance that resembles cloves. The flowers eventually get small, green fruit that turns black when ripe. Russian vine is a hardy plant that is easy to grow and can tolerate a wide range of growing conditions.

It is often used to cover the ground or as a climbing, plant to cover walls or fences.

6. Bistorts (Bistorta Amplexicaulis)

Bistorta Amplexicaulis
Dinesh Valke Bistorta Amplexicaulis

Bistorta amplexicaulis, also known as American bistort or mountain bistort, is a flowering plant native to North America. It belongs to the family Polygonaceae, which also includes Japanese knotweed (Fallopia japonica).

Bistorts is a perennial plant that grows to about 1-3 feet. It has solid and hairy stems and leaves that are long, narrow, and lance-shaped. The flowers are pink or rose-colored and sit in spike-like clusters.

While Bistorta amplexicaulis and Japanese knotweed belong to the same family, they have several distinguishing characteristics that help you differentiate between them. Bistorta amplexicaulis is native to North America, while Japanese knotweed is native to Asia.

Bistorta amplexicaulis has solid, hairy stems and pink or rose-colored flowers, while Japanese knotweed has hollow, bamboo-like stems and tiny white flowers.

Japanese knotweed is a much larger plant than Bistorta amplexicaulis, reaching heights of up to 10 feet (3m), while Bistorta amplexicaulis grows to a height of only 1-3 feet (0.3 – 0.9 m).