Reynoutria japonica

This plant is called Japanese knotweed.

It grows in East Asia. It has hollow stems. These stems look like bamboo.

The plant has very strong roots. These roots can grow through cracks in roads. They can even grow under buildings.

Knotweed grows very fast. It can crowd out other plants. It can grow in many places.

Some people eat the young stems. They taste like lemons. It is a very tough plant.

Japanese knotweed is a plant from East Asia. It grows in Japan, China, and Korea.

The plant has hollow stems. These stems have raised nodes. This makes them look like bamboo.

The leaves are broad and shaped like a heart. New leaves are often dark red. Older leaves turn green.

This plant is an invasive species. This means it moves into new areas and causes trouble. It grows in many places, like roadsides and waste areas. It is very strong. It can grow in dry soil or salty soil.

Its roots, called rhizomes, grow deep and wide. These roots can grow through cracks in concrete or brick. They can even reach building foundations. This can cause damage to walls and roads.

Because it grows so thick, it crowds out other plants. This can change the local nature. In the UK, it is even against the law to let it grow in the wild. Some people find it useful. Beekeepers like it, and some people eat the young stems. They taste like lemony rhubarb.

Japanese knotweed is a very strong plant. It belongs to the knotweed and buckwheat family. This plant is native to East Asia, including Japan, China, and Korea.

Today, it grows in many new places. It is found in North America and Europe. Many countries call it an invasive species. This means it moves into new areas and causes trouble for the local nature. It can grow in many different spots, like roadsides and waste places.

The way this plant works makes it hard to stop. It has hollow stems with raised nodes. These nodes make the plant look like bamboo. The leaves are broad and shaped like a heart or a shield.

The plant grows in thick, dense groups. This growth shades out other living things. It can even crowd out all other plants in an area. The plant is very tough. It can live in dry soil or salty soil. It can even survive in different types of soil pH.

People have studied this plant for a long time. An adventurer named Philipp Franz von Siebold moved the plant from a Japanese volcano. He brought it to the Netherlands. By 1850, a specimen was given to the Royal Botanic Gardens, Kew.

In the 1970s, Ann Conolly wrote the first big study on its history. She looked at how it spread in the UK and Europe. The plant moved fast using rail and water networks. In the UK, many plants are actually just one single female clone.

This plant can cause big problems for buildings. Its roots, called rhizomes, grow very deep and wide. These roots can grow through cracks in concrete, asphalt, or brick.

They can even damage building foundations and walls. This can be very expensive to fix. In the UK, it cost £70 million to remove the plant from the London 2012 Olympic site. In the US, it is found in 42 of the 50 states. It is even found in almost all provinces in Canada.

Even though it is a pest, some people use it. Beekeepers like the plant. Some people also eat the young stems. They say the stems taste like lemony rhubarb. Scientists are even trying to use a tiny insect to help. This insect is called the Japanese psyllid. It eats only this plant. Researchers started testing these insects in South Wales in 2016. They hope this will help control the plant in the wild.

Reynoutria japonica is a herbaceous perennial plant. It belongs to the Polygonaceae family, which includes knotweed and buckwheat. This plant is native to East Asia, specifically Japan, China, and Korea.

Today, it is found throughout Europe and North America. Many countries classify it as an invasive species. This means it establishes itself in new habitats and causes problems for local ecosystems. It is often called Japanese knotweed or Asian knotweed.

The physical structure of the plant allows it to grow very aggressively. It features hollow stems with distinct raised nodes. These nodes give the plant an appearance similar to bamboo, though they are not related.

The leaves are broad and oval with a truncated base. They can look like a flattened heart or a shield. New leaves often appear dark red and long. As they mature, they turn green and grow to a larger size.

The plant grows in a zigzag pattern where leaves shoot from the stem nodes alternately. Mature plants form dense, thick colonies that can crowd out other species.

Several mechanisms make this plant extremely difficult to manage. It has a powerful root system made of rhizomes. These rhizomes can extend both horizontally and deep into the ground.

They are resilient enough to survive very low temperatures. The plant is also highly tolerant of diverse environmental conditions. It can survive droughts and different soil types. It can even handle high salinity and various soil pH levels. Even when the plant is cut down, it can vigorously resprout from its roots. In some areas, like British Columbia, excavators have dug to a depth of three metres to remove it. Despite this, the plant grew back twice as large the following year.

History shows how the plant spread across the globe. An adventurer named Philipp Franz von Siebold moved the plant from a Japanese volcano to the Netherlands. By 1850, a specimen was donated to the Royal Botanic Gardens, Kew. Gardeners originally favored the plant because it looked like bamboo. It was easy to grow everywhere. In the 1970s, Ann Conolly provided the first authoritative work on its history in the UK and Europe.

The plant traveled rapidly by using rail and water networks. In the United Kingdom, the plant is often a single female clone. However, it can still hybridize with related species.

The economic and structural impact of the plant is significant. Its roots can penetrate cracks in concrete, asphalt, and brick. This can damage building foundations, walls, and drainage systems.

While some reports suggest damage only occurs near already compromised areas, the costs remain high. In the UK, removing the plant from the London 2012 Olympic site cost £70 million. A national eradication program in Britain would cost an estimated £1.56 billion. The plant also affects the housing market. In the UK, some lenders have refused mortgages if knotweed is found on a property. Some homeowners may even be unable to sell their houses due to its presence.

There are many plants that people sometimes confuse with Japanese knotweed. These include dogwood, lilac, and Himalayan balsam. Other similar species include bindweed, bamboo, and Russian vine.

Despite its status as a pest, the plant has some uses. It is popular with beekeepers. Some people also forage the young stems as a vegetable. The flavor is often described as being like lemony rhubarb.

Scientists are looking for biological ways to control the spread. In 2010, the UK decided to release a Japanese psyllid insect called Aphalara itadori. This insect has a diet that is highly specific to Japanese knotweed.

Controlled release trials for this insect began in South Wales in 2016. This represents a form of classical biological control. By using a natural predator, researchers hope to manage the invasive populations more effectively without relying solely on chemicals.