The Japanese invasion could not kill the species and how it conquered different parts of the planet

“After sending several baskets of plants season after season to a friend, they were all unsatisfactory. explained Botanist John Wood in 1884. He was writing a garden manual and heaped praise on a sensational new shrub that even the most unlucky horticulturist could handle. It is a Far Eastern import with nice red budsHeart-shaped, beautiful foliage And the stems are beautifully curved.

In short, Wood has nothing bad to say about the plant, and if you let it grow for a few years, it will develop “Beautiful Bush”.Of course, it’s no ordinary shrub: a Japanese knotweed (Japanese knotweed) In a startling detail that Wood fails to mention.

Aside from its classic aesthetic qualities, if perhaps a little too much, it’s wicked good value because once you have it, it’s (almost) permanent: will never dieAnd without drastic action, future generations They will fight against the forest Thick stems for centuries.

Of the 13,000 alien species that have roamed the globe since colonization began in the 15th century, Japanese knotweed is considered one of the most complex: It suffocates suburban gardens, submerges entire railroad tracks, and floods canals and national parks.

If the invasive bush is allowed to grow at will, it could soon take over the whole of England except for shady patches where trees exist, says Dan Eastwood, professor of biological sciences at Swansea University in the UK. “There shall be a common dominion”It says.

But the complete removal of this weed is very difficult and basically consists of extracting the soil: Dig at least 5 meters deep and disposes of the entire block almost as if it were radioactive. If any remain, it can return again and again, regenerating from small pieces, and ambushing gardeners for up to 20 years after it’s gone. One study found that the bush could regrow from just 0.3 grams of root clippings, the weight of a pinch of salt.

Unfortunately, you can’t put a little weed killer in it. “Even though it seems dead it grows again”, says Kevin Callaghan, director of London-based eradication firm Japanese Knotweed Specialists. 10-foot tall monocot weeds are not good for the garden, and not good for wildlife. Even the infection of this bush May have financial consequences Disaster.

In England, a single existence A lien can instantly reduce a home’s value by 5% to 15% And many banks will reject the mortgage. How did Japanese knotweed manage to become so surprisingly tough? Will we ever figure out how to beat it?

On August 9, 1850, Kew Gardens in London received a surprise package in the mail. Unexpected The gift contained many unusual plants And a note revealing the identity of the mysterious benefactor: Philipp Franz Balthasar von Siebold, a German physician and botanist.

Von Siebold had recently returned from the Japanese territory of Tejima, a trading post built on an artificial island off the coast of Nagasaki. During the isolated Edo period, it was the country’s only point of contact with the outside world The country closed its borders to foreigners for more than two centuries.

As a renowned physician, von Siebold had unprecedented access to various contacts in Japan and used them to indulge his interest in plants: He had people collect samples from all over the country. But after a rare visit to the mainland and an unfortunate incident involving a banned map found in his luggage by local authorities, he was finally asked to leave.

then, Von Sieboldt packed about 2,000 plants and returned to Europe. This includes a wonderful and widespread shrub found in Asia, including Japan, Taiwan and South Korea, valued for its uses in traditional medicine and, interestingly, as a vegetable. When cooked, its fresh shoots have a crisp, tart flavor similar to rhubarb.

soon, Von Siebold & Company of Leiden was born, specializing in the sale of plants from the Far East. Based in the Netherlands. And from the first moment, Fallopian japonica is one of its star plants. It was only natural that this vigorous beauty should be shared with others, and Kew Gardens received its own specimen. From there, his success was rapid.

Japanese knotweed wins And, within a few decades, it had sunk its roots deep into the ground in much of Oceania, North America, and Europe. Many of these 19th-century clusters still exist today, in the same locations where they were planted. This plant is said to outlive both the garden and the gardener.

According to Eastwood, this early popularity was the first clue to his formidable offensive powers. “The truth is that it was brought to this country and planted extensively over a considerable period of time, from the Victorian era,” he says. “So when you’re talking about the number of individuals, you’re putting in the ecosystem before it’s established. [allí]Humans really played a big part in that.”

However, outfielders don’t deserve all the credit. There is a bush Truly exceptional – an alien invader truly out of this worldFrom the wasteland of volcanoes and poisonous gases. The plant’s natural habitat is the slopes of volcanoes, which is one of the first to settle after an explosion. can sink Its famous unstoppable roots in rock Solid, fresh volcanic rock, with stems and leaves above ground buried in glowing magma, can lurk for years.

Away from this harsh environment, in the paradise of the average suburban garden, these natural adaptations are almost impossible for the plant to overcome. This story is the secret of their steadfast expansion and impressive survival. “Every year when Photosynthesis begins and The plant captures light energy, take that resource and put it underground,” says Eastwood. The surface parts shrivel up and die each winter, but its rhizomes — a kind of twisted, modified stem — are still there, retaining the sugar it produces when they’re all good.

The following spring, the plant sends out new roots to extend its range laterally, and these produce more underground stems. In this way, until it slowly progresses Monopolized every available inch of space. This two-part system is very difficult to control with chemicals because the body parts are above and below ground. Very useful GlyphosateIt works by blocking the enzyme that plants need to make amino acids, and the best way to use it is paradoxically.

As many owners have discovered in their quest to eradicate it, if you use too much, it will The plant is randomly propagated.The part you see above the ground is the crown: this is the dominant part of the plant that actively stores energy. But he has support. “There are dormant shoots around those crowns, so they could stimulate new growth, but they don’t because the crown suppresses them,” says Eastwood.

So if you fill one of these weeds with herbicide, You can kill the crown entirely Suddenly all its satellite buds arise.

Von Siebold did not know when the first model was sent to London would go on to become one of the greatest villains in botanical history. Unfortunately, Japanese knotweed isn’t the only invasive plant with a bright future to overwhelm vast swaths of the planet. In fact, two other major weeds currently worrying landowners, governments and environmentalists share some startling similarities.

Heracleum montagecianum arrived in England in 1819 after seeds were sent to Kew Gardens from the Caucasus Mountains in Russia. today, Its tall stems and white flowers are found throughout Europe and North AmericaClose to highway shoulders, railroad tracks and water bodies.

As well as being invasive, it’s highly toxic – no doubt regularly making headlines after visitors suffer severe blisters and chemical burns from its sap. Impatiens glandulifera arrived two decades later, after a surgeon from India sent specimens to the Horticultural Society of London. Soon became a popular plantAppreciated for its delicate pink orchid-like flowers and dense foliage.

But within a few years it had escaped into the wild, by the turn of the century It was already considered a weed. Along with many others such as Japanese knotweed and rhododendrons, these plants are at the forefront of a gradual adaptation of botany. Native plants For those who are hard to control. And the story is far from over. The 19th century was the era of elaborate plantations and Importation of unregulated plants In hindsight, many plants found in millions of backyards around the world are considered invasive.

Eastwood is willing to bet next A major invader would be the Japanese anemone. With saucer-shaped pink, purple or white flowers on slender stems, this member of the butterfly family is popular for adding color to gardens in late summer.

But like Knotweed, it can easily spread underground and take over quickly. Perhaps people don’t care much about such a handsome invader; It is certainly difficult to imagine their presence reducing the value of a property. But if that happens… let’s say we asked here first.

* By Zaria Corvette

BBC World