Three-cornered leek (Allium triquetrum)

Identifying Allium triquetrum

Three-cornered leek bears drooping clusters of white flowers with delicate green markings on upright stems 20-40cm high, above slender green leaves which are broad and grassy in appearance. At first glance it can look like a white-flowered bluebell, but its oniony smell makes the two plants easy to tell apart. If harvesting three-cornered leek from the wild, take great care not to confuse it with bluebells – which come in white as well as blue forms – and are toxic if eaten. Other toxic plants that may be confused with three-cornered leek include lily of the valley, which has large, broad leaves and nodding, bell-shaped flowers, so make sure you are certain of your identification before harvesting. Three-cornered leek may also be mistaken for wild garlic, which has shorter, broader, oval-shaped leaves. While edible, three-cornered leek has a milder flavour than wild garlic, so may not yield the desired results in the kitchen. The leaves have the mildest flavour but the stems can be used as a substitute for spring onions, and the flowers in salads.

As its name suggests, three-cornered leek has triangular stems and leaves, which makes it easy to identify from most other allium species (the only other plant with triangular-shaped leaves and stems is few-flowered leek (Allium paradoxum), which is also a non-native, invasive plant. If you cut through a leaf or stem at the base, its 'three corners' are clearly visible.

Where do three-cornered leeks grow?

Three-cornered leek started its spread in Cornwall in the 1850s and is now found growing throughout the UK, though mostly in milder regions (after all, it is a native of the Mediterranean). It's found growing extensively in coastal areas, on hedge banks, verges and in churchyards.

Is Allium triquetrum invasive in the UK?

Allium triquetrum is listed as an invasive non-native species under Schedule 9 of the UK Wildlife and Countryside Act. This means it's an offence to cause it to grow in the wild, either by dumping garden waste, planting it or growing it where it can escape from a garden into the wild. Because of its quick-spreading and invasive nature, it's not advisable to plant three-cornered leek in gardens, even though it's not an offence to buy or sell it.

How do you get rid of three-cornered leeks?

Because three-cornered leek spreads by both bulbs and seeds, getting rid of it takes persistent hand-weeding to dig up the bulbs, as well as removing the faded flower heads before they mature to produce seeds. Of course, treating three-cornered leek as a crop is another way to restrict its spread.