Many people think of plants as pretty green plants. While they are important for keeping the air clean, they are simple organisms. A major shift in research is shaking up the way scientists think about plants: they are much more complex and more like us than you might think. This thriving field of science is too exciting to do justice to in just one or two stories.

This article is part of the Plant Curious series, which examines scientific studies that challenge your view of the plant world.

Himalayan balsam is native to the western Himalayas and was brought to Britain in the 19th century by plant hunters who liked its pink, orchid-like flowers and exploding seed pods, which can hurl seeds up to seven metres.

This plant escaped from gardens and spread along the British river network, where it formed dense swathes along river banks. Himalayan balsam also successfully invades forests. It is the tallest annual herb in Britain, growing up to four metres tall. However, in its native range Himalayan balsam only grows half that height. In summer, British conservationists engage in ‘balsam bashing’ to stop its spread.

When we see plants in the wild, we may not think about what is happening beneath them. For example, many plants form relationships with fungi and bacteria that can provide them with nutrients that might not otherwise be available to them.

When an alien plant species arrives in a new environment, the soil community may be different from its native environment. Some of these plants respond by altering the soil to promote their own growth.

Himalayan balsam does this by reducing the number of mycorrhizal fungi – the fungal species that form mutually beneficial relationships with other plants below and above ground. It changes the bacterial community in the soil and some of the fungal community above ground. When Himalayan balsam grows in soil that it colonized the previous year, it grows faster and larger, which scientists have linked to these fungal and bacterial changes. And even if you remove Himalayan balsam, native plants often don’t grow as well in that soil.

Other examples of monster plants in the UK are Rhododendron (Rhododendron ponticum), an invasive plant from southern Europe and southwest Asia that grows up to eight meters tall and thrives in forests and shades native plants. Rhododendron hosts two deadly pathogens, Phytophthora ramorum And P. kernoviaethat attacks the native trees of Great Britain.

Japanese knotweed (Japanese Reyneuria), a monster from Asia that reproduces by cloning and can grow back from a fragment weighing just 0.3 grams (about the weight of a pinch of salt). This plant can cause so much damage to buildings that British homeowners must declare in their legal documents if there are any traces of this plant on their property when selling their home.

Giant Hogweed (Heracleum mantegazianum), native to Central Asia, can grow up to five meters tall, with each plant producing about 20,000 seeds. Giant hogweed secretes poisonous sap as a defense mechanism. This sap causes severe skin blisters and burns that can last for months or even years.

Monsters all over the world

As humans spread across the world, the species they brought with them also increased. Monster plants are a problem on every continent on Earth. Invasive plant species can even be found in Antarctica.

Pines were introduced to southern Africa as timber following European colonisation in the 1650s. South Africa is already prone to drought, but a single pine tree uses 20% more water than native plant species. For some rivers, pine invasion upstream can reduce natural flow by as much as 45%, meaning less water for people and ecosystems.

Kudzu (Pueraria montana) is a climbing plant from Japan and China that was introduced to the United States in the 19th century to prevent soil erosion. It can grow up to half a meter a day and smothers grasses and other plants, including trees, with its creeping vines that can grow up to 30 meters long. In her novel The Color Purple, Alice Walker wrote, “Racism is like that local creeping kudzu vine that devours whole forests and abandoned houses.”

Broom (Ulex europaeus) is native to continental Europe and Britain, but was introduced outside its original range mainly in the 19th century as a nostalgic ornamental and hedging plant in several European-colonized countries. This woody, thorny shrub can grow up to seven meters tall in its introduced range, compared to only two and a half meters in its native habitat. Gorse increases the risk of fire in Chile, reduces the growth of tree seedlings in New Zealand, and acidifies the soil, stopping the growth of rare plants in British Columbia, Canada.

Mesquite (Prosopis sylvestris), also known as the “devil tree” in infested areas such as India and parts of Africa, is native to Mexico and parts of South America. This species has been introduced outside its natural range as firewood and livestock fodder, but grows quickly to heights of up to 12 meters. It has large thorns and low branches that form impenetrable thickets and overgrow pastures and wetlands. Livestock that eat large quantities of its seed pods become poisoned and often lose their teeth due to the high sugar content of the pods. In dry, arid regions with water shortages, the mesquite’s root system absorbs water more quickly than that of native plant species.

For all these different reasons, invasive alien species are one of the biggest causes of native species loss worldwide. However, eradicating these plants is a difficult and expensive task. For many species, the best we can do is reduce their size and distribution.

The most effective strategy, of course, is to prevent alien species from arriving in the first place. Today, many of the alien plants growing wild in the UK have escaped the horticultural trade, so choose native plants for your garden and for gifting.

And if you like something a little more exotic, botanical gardens offer a wonderful opportunity to enjoy the extraordinary plant diversity without damaging the local habitat.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Zarah Pattison receives funding from NERC, UKRI.