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Blossoming Invaders: Spring’s unwelcome guests on the UK scene 

Blossoming Invaders: Spring’s unwelcome guests on the UK scene 

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As the vibrant colours of spring are just about to paint our UK landscape, we all eagerly anticipate the blooming of our favourite flowers. However, amidst the excitement of seasonal renewal, there is a lurking concern— the invasive plants that threaten to disrupt the harmony of our ecosystems. Spring brings not only the promise of new growth but also the challenge of managing and controlling the spread of invasive species.  

In this blog, we will list some of the biggest threats to look out for this Spring and give you some tips on how to identify them.  

Japanese knotweed

Japanese knotweed

Introduced to the UK during the Victorian era, Japanese knotweed (Reynoutria japonica) was initially admired for its aesthetic appeal, resilience, and regenerative qualities. However, over time, this non-native species has transitioned from a once-praised plant to a notorious invader. Its aggressive nature poses a threat to native vegetation, and its capacity to cause damage in urban environments is now widely acknowledged, marking Japanese knotweed as a problematic and invasive species. 

Recognising Japanese knotweed in early spring can be challenging as the appearance of the plant varies depending on the age and any previously applied herbicide treatment. In late winter and very early spring months, you can identify it by looking for brown stems that resemble bamboo left standing or broken on the ground. During Spring, new shoots of Japanese knotweed will develop, looking like red asparagus. They start as red buds and grow rapidly, a few centimetres each day, quickly overtaking nearby plants. On warmer days, mature plants can grow as much as 10cm per day. 

Find out more about Japanese knotweed

Himalayan Balsam

Himalayan Balsam

Himalayan balsam (Impatiens glandulifera) is an invasive plant species that originated from the Himalayan region and was introduced to the United Kingdom as an ornamental garden plant in the 19th century. It is also known by various other names, including Indian Balsam, Policeman’s Helmet, and Kiss-me-on-the-mountain.

This plant causes significant ecological challenges. It competes aggressively with native plants, diminishing biodiversity and disrupting ecosystems. In areas with big infestations, it can also lead to erosion and flooding.

During spring, Himalayan balsam seedlings start to appear as early as February. The fleshy stems and leaves are mostly green and grow to around 2m tall by May, when the nodes turn red. It’s normal to see the plants in large numbers as seed pods from the previous year produce thousands of viable seeds.

Find out more about Himalayan Balsam



The invasive herbaceous perennial plant known as Field or Common horsetail, scientifically named Equisetum arvense, goes by various other names such as snake grass and puzzle grass. It is occasionally mistaken for Marestail.

Field horsetail holds a remarkable place in history, with its ancestry dating back a staggering 350 million years, making it one of the oldest surviving plants on Earth. Beyond its historical significance, people have used it since ancient times for medicinal purposes. However, caution is warranted, as the plant is poisonous to livestock, particularly horses when consumed in large quantities.

When left unchecked, Common horsetail can rapidly form extensive clusters, taking over local habitats. This specific variety is widespread across Britain, commonly found on roadsides, in gardens, on paths, brownfield sites, and wasteland.

Come spring, usually in March and April, Horsetail comes to life, initiating the production of spore-containing cones. These structures, approximately a centimetre in length, are attached to fertile striped, brown stems that sprout from the ground.

The spring growth originates from the rhizomes underground, which have remained dormant throughout the winter as well as the spores. The new shoots emerge like small green bottle brushes, that can grow to around 1m tall.

Find out more about Horsetail



Montbretia (Crocosmia x crocosmiiflora), bred in the 1880s and introduced to the UK via France, has its origins in South Africa. A beloved garden plant, it’s especially common in western parts of England, Wales, and Scotland. Distinguished by its fleshy underground corms, which serve as storage organs and initiate growth like bulbs..

Because Crocosmia x crocosmiiflora is deemed invasive, other Montbretia varieties make better choices for gardeners. It is often difficult to tell one variety from another until they flower.

Growth is usually visible between February and November. Montbretia leaves are long and narrow, emerging from the base of the plant. There can be between 6 and 12 leaves for each corm, and they grow to around 60 centimetres.

Find out more about Montbretia

Three-cornered leek

Three-cornered leak

Three-cornered leek (Allium triquetrum) is a bulbous perennial plant that belongs to the onion family, Alliaceae. It is also known by various other names, including three-cornered garlic, and angled onion. Native to the Mediterranean region, three-cornered leek has spread to other parts of the world and is considered an invasive species in the UK.

The plant gets its name from its distinctive triangular-shaped stem. It produces narrow, strap-like leaves that are often three-angled, and its white, star-shaped flowers are arranged in umbrella-like clusters at the top of the stem. The plant has a strong garlic or onion scent, and it is edible. However, caution is advised when foraging for wild plants, as it can be easily confused with toxic plants like bluebell bulbs.

Three-corned leek grows from a bulb. Its leaves can be found from late autumn onwards and it flowers in early spring – the exact timing depends on weather conditions and in some areas, it is a very early flowerer.

If you discover any of these plants on your property, don’t wait for them to grow any bigger, just nip it in the bud and contact Environet’s team today on 01932 868 700 or email us at [email protected]

Robert Spaceman

“We had a large stand of bamboo removed, thinned, contained and replaced. The customer service has been first class. Joe and Jason were fabulous and kept me well informed at all times”.