Invasive edibles: three-cornered leek

There is a lot to like about the three-cornered leek (Allium triquetrum) — not only can it be foraged throughout the winter and early spring but all parts of this invasive edible can be eaten. Use it freshly wilted or in a range of dishes as an alternative to leek or chives

Three-cornered leek

In the same way as the snowdrop (Galanthus spp) is a symbol of early spring, three-cornered leek (Allium triquetrum) is one of the first edibles to herald the start of a new foraging calendar. The two plants are not wildly dissimilar in appearance — with their long, thin, green leaves and bell-shaped white flowers — and three-cornered leek is also known by the similar-sounding common name of snowbell. Unlike the poisonous snowdrop, however, the three-cornered leek is an allium family and is far more than just an attractive ornamental — it offers foragers a really useful wild alternative to leek, spring onion or chives.

Three-cornered leek flowers showing their green stripes
Three-cornered leek flowers have green stripes

Both three-cornered leek and the snowdrop enjoy similar habitats in hedgerows and woodland clearings and could possibly be confused — although three-cornered leek is a much larger plant, growing to around 17cm-60cm high, compared to the snowdrop’s 7cm-15cm. Three-cornered leek might also be mistaken for other woodland natives such as the bluebell (especially the white bluebell, or before flowering) or its fellow invasive edible allium few-flowered garlic (Allium paradoxum).


What distinguishes three-cornered leek from its poisonous lookalikes is the green base to tip stripes on its petals, the distinct keel-shape of the leaf when viewed in cross-section, as well as an onion-smell when crushed. It shares many features with other alliums, including forming bulbs and having umbel flowers on a leafless stem.


While this hardy plant may seem at home on the UK’s banks, verges and woodland edges, it is an introduced species. Three-cornered leek is a native of the central Mediterranean and became naturalised in the UK sometime after its introduction in the late 19th-century. It has also been introduced to North and South America and to Australia and New Zealand, where it is known as onion weed or angled onion.


An easily-spread invasive

Unlike its fellow introduced species, the snowdrop, which has been welcomed into the woods, the three-cornered leek is considered an invasive under schedule 9 of the Wildlife and Countryside Act 1981, meaning it is an offence to plant it or cause it to grow in the wild. The plant’s seeds are easily spread by ants and where it grows it can become prolific, crowding out native species such as the bluebell and primrose. One of its ecological advantages is that it appears while other plants are dormant, with new growth emerging from bulbs as early as October.

Three-cornered leek
Where three-cornered leek grows it can become prolific

The advantage of an invasive edible is that harvesting the plant is actively encouraged and fortunately all parts of three-cornered leek have a culinary use. The bell-like flowers typically appear in March or April and can be used in salads. The leaves are best eaten from November to early spring, when they are at their fullest flavour before flowering starts. Their flavour is mellowed by cooking, so they are best served raw or lightly wilted. The young plants can be pulled up and used whole in the same way as a spring onion, while the young seed pods can be pickled. But remember, even though it is invasive, you will still require the landowner's permission to uproot it.


Allium plants are known to inhibit the growth of micro-organisms including bacteria, fungi, viruses, and parasites. These properties come from the substance allicin, which contains sulphur, and gives alliums their distinctive odour (Arifa et al, 2020). While many alliums have been investigated for their medicinal and health benefits, especially garlic (Allium sativum), there is no direct evidence for three-cornered leek having any clinical applications — although one study did show its leaf had a 95% inhibitory affect on growth of Ceratocystis sp, a fungus that causes fruit rot disease (Suprapta, 2016).


One note of caution is that alliums can cause poisoning in pets, inducing anaemia. Both dogs and cats seem especially susceptible, although tortoises have also been reported to have been poisoned after eating wild garlic (Veterinary Poisons Information Service, 2020) — worth remembering if you have pets and are considering planting alliums in your garden.


Discover more wild edibles and recipes on a foraging course and read more about three-Cornered Leek here.


References


Arifa, F., Fajrina, A., Eriadi, A., & Asra, R. (2020). Antimicrobial activity test of genus alium: A review. International Research Journal of Pharmacy, 11(12), 17–25.


Suprapta, D. N. (2016). A review of tropical plants with antifungal activities against plant fungal pathogens. www.preprints.org.


Veterinary Poisons Information Service. (2020, January 2). Allium poisoning - not just cats and dogs are at risk.


Always stay safe when foraging. You need to be 100% sure of your identification, 100% sure that your foraged item is edible, and 100% sure that you are not allergic to it (it is good practice to always try a small amount of any new food you are consuming). If in doubt, leave it out!