Allium triquetrum is a bulbous flowering plant in the genus Allium (onions and garlic) native to the Mediterranean basin. It is known in English as three-cornered leek (or in New Zealand as onion weed); both the English name and the specific epithet triquetrum refer to the three-cornered shape of the flower stalks.
Allium triquetrum is native to south-western Europe, north-western Africa, Madeira and the Canary Islands, where it grows in meadows, woodland clearings, on river banks and roadside verges from sea level to an altitude of 850 metres (2,790 ft). It has also been introduced to the British Isles, New Zealand, Turkey, Australia, California, Oregon, and South America.
Allium triquetrum produces stems 17-59 cm (6 34-23 14 in) tall, which are concavely triangular in cross-section. Each stem produces an umbel inflorescence of 4-19 flowers in January-May in the species' native environment. The tepals are 10-18 mm (1332-2332 in) long and white, but with a "strong green line". Each plant has 2-3 narrow, linear leaves, each up to 15 cm (6 in) long. The leaves have a distinct onion smell when crushed.
All parts of the plant, from the bulb to the flowers, are edible fresh (for example in pestos) or cooked, with "a subtle flavour like leek or spring onion".