Three-cornered leek removal

Not sure how to deal with Three-cornered leek? We’re here to help with advice and provide a complete removal package

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What is
Three-cornered leek?

Three-cornered leek, scientifically known as Allium triquetrum, is a perennial plant with a bulbous structure that is part of the onion family, Alliaceae. Also recognised by names such as “Three-cornered garlic” and “Angled onion”, this plant originally comes from the Mediterranean region but has spread to different parts of the world, becoming an invasive species in the UK.

Identified by its unique triangular stem, Three-cornered leek produces slender, strap-like leaves that are often three-angled. Its white, star-shaped flowers form clusters resembling umbrellas at the top of the stem. Emitting a garlic or onion fragrance, the plant is edible. However, caution is advised during wild plant foraging, as Three-cornered leek can be easily mistaken for other bulbous poisonous plants such as English bluebell.  

Three-cornered leek grows from a bulb, with its leaves visible from late autumn onward. The flowering occurs between April and June, although the precise timing depends on weather conditions, making it an early bloomer in some areas.

What does it look like?

Three-cornered leek, belonging to the Allium genus (which includes onions and garlic), is a bulbous flowering plant originating from the Mediterranean basin. During the spring season, this bulb blooms with bell-like white flowers measuring around 2cm (10-18mm) in diameter. These flowers adorn stems that are three-sided and approximately 30cm tall.

The leaves of the Three-cornered leek are notably angled, appearing in groups of three at the base of each plant. From April to June, these distinctive flowers thrive in various locations such as woodlands, meadows, gardens, and long verges. When the leaves are crushed, they emit a discernible onion fragrance.

Find out more about the plant by checking our Three-cornered leek Identification page.

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What damage is caused by Three-cornered leek?

The invasive nature of Three-cornered leek has led to several negative impacts on the UK’s native ecosystems. It can outcompete native plant species for light, nutrients, and space, reducing biodiversity.

Due to its invasive status, efforts have been made to control and manage Three-cornered leek in the UK. Various methods including manual pulling, herbicide treatment, and excavation, have been used to control its spread. Of course, choosing the right technique depends on the size of the infestation.

It is an offence under Schedule 9 of the Wildlife and Countryside Act in England and Wales to plant or otherwise cause this species to grow in the wild.


Changes in plant composition and habitat structure can affect wildlife that relies on specific plant species for food and shelter. Invasive plants like Three-cornered leek may not provide the same resources or support for local fauna.

Soil degradation

Invasive plants can alter soil properties and nutrient cycling. The presence of Three-cornered leek may influence soil characteristics, potentially affecting the growth of other plants in the area.

Habitat alteration: 

The aggressive growth of Three-cornered leek can alter natural habitats. Its dense colonies can crowd out other plant species, leading to changes in the composition and structure of local plant communities.

Competition with cultivated plants

In agricultural settings or gardens, Three-cornered leek may interfere with cultivated plants. Its aggressive growth and ability to form dense stands can compete for nutrients, water, and sunlight with desired crops or ornamental plants.

Legal implications

Three-cornered leek is listed on Schedule 9 of the Wildlife and Countryside Act, meaning that you must not put it in your green waste collection and should check whether your local recycling centre will accept it before taking it there.

You can burn the plant on your property subject to local bylaws or ask a registered waste carrier to take it to a tip that will accept it.

Use our extensive guide to identify Three-cornered leek

What does Three-cornered leek
look like?

Prevent costly damage to your property

How can I control
Three-cornered leek?

There are several methods which you can consider removing the plant, such as hand pulling or mulching. However, these methods depend on the size of the infestation, and it might be difficult to know which method will be the most effective, especially when the plant is at high risk of regrowth.

For larger or particularly stubborn infestations, it is always best to talk to the professionals. At Environet, we use a wide range of techniques to control or eradicate Three-cornered leek from your property. These methods include hand pulling, mulching, herbicide treatment and excavation.

Hand pulling

For new plants, hand pulling can be an effective, low impact control solution. The downside is that it can be time consuming, and bulbs or seeds may get left behind in the soil, so follow up monitoring to check for regrowth is important.


Another minimal impact method is known as mulching. Immature and semi mature bits of Three-cornered leek are cut to ground level. The areas are then heavily mulched to prevent regrowth.

Herbicide treatment

Herbicide treatment can also be considered; however, it can be a rather blunt instrument: as it will likely kill other non-target plants, particularly in garden settings. For large areas, where the vast majority of plants are “target” plants, herbicide is usually the most effective option.  

Mechanical excavation

Excavating the soil that is contaminated with the bulbs and seeds is the fastest, and surest way to remove Three-cornered leek infestations. The fact that the seeds are windborne often means you will find Three-cornered leek growing in hard-to-reach places in walls and crevices. To avoid excessive damage to surrounding structures, using herbicide in conjunction with excavation is often a sensible approach.


If you would like advice or a quote, please give our friendly team a call today.

With over 25 years’ experience in the industry, Environet is the UK’s leading invasive plant removal company. During this time, we’ve dealt with some of the UK’s most common non-native invasive plants including Japanese knotweed, Bamboo, Giant hogweed and, of course, Three-cornered leek.

We specialise in helping both homeowners and developers across the UK, as well as organisations such as councils and housing associations.

Whether you need to identify a potentially invasive plant or need professional removal, contact the team at Environet today.

To Start Fixing your Three-cornered leek Problem Today

Call our team for specialist advice and effective solutions


We have robust systems in place for Environmental and Health & Safety management. Risk assessments are carried out for every aspect of our business to identify situations where harm could be caused. We have an ethos of continuous improvement to eliminate or reduce the risks with detailed working procedures, on-going training and monitoring.

All our staff have health and safety and emergency first aid training. We are also accredited by CHAS and Constructionline and are members of the Property Care Association (PCA).


Our team of experts is available between 9am and 5:30pm, Monday to Friday to answer your enquiries and advise you on the next steps

Want a survey?

Request a survey online in less than two minutes by simply uploading a photograph and providing a few brief details. A member of the team will swiftly come back to you with further information and our availability.

Need quick plant identification?

Simply upload a few images of your problem plant to our identification form and one of our invasive plant experts will take a look and let you know, free of charge what you are dealing with. We’ll also be there to help with next steps where necessary. 

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