threecorner leek

Scientific name: Allium triquetrum

Verified common names: three-cornered leek, three-cornered garlic

Family: Liliaceae (historical placement); many modern treatments place Allium in Amaryllidaceae, subfamily Allioideae

Genus: Allium

A bulbous perennial with a clumping habit, three-cornered leek typically forms low patches of foliage and flowering scapes. Plants often produce one to a few erect, triangular (three-angled) flowering stalks arising from small bulbs. Flowers are borne in loose, nodding umbels of several bell-shaped blooms; each flower typically has six white tepals with a distinctive green midrib and may appear pendent. Leaves are usually basal, straplike and smooth, often appearing as a pair or a few leaves per bulb; they are generally flat rather than hollow and emit a mild onion/garlic scent when crushed. Distinctive features include the three-angled flower stalk (hence “three-cornered”), the nodding white bells with green midribs, and the onion-like aroma. Seasonal variation: in mild Mediterranean-type climates the plant commonly flowers from late winter into spring, with leaves present through the flowering period and senescing afterward.

Three-cornered leek typically grows in shaded to semi-shaded sites with moderate moisture. It is often found in gardens, woodlands, riparian corridors, hedgerows and other disturbed or semi-natural habitats where soils are reasonably fertile and not excessively dry. The species is commonly naturalized in parts of California and Oregon and is originally native to the western Mediterranean region. It tolerates a range of soil types but is often associated with damp, well-drained soils and sheltered microsites.

Flowers provide accessible pollen and nectar to a variety of generalist pollinators, including bees and other insects that visit small, bell-shaped Allium flowers. The bulbs and leaves produce sulfurous compounds that give an onion/garlic odor; this chemistry contributes to interactions with herbivores and microbes and may reduce grazing by some mammals.

Leaves and bulbs of Allium triquetrum are often regarded as edible in regions where the plant is familiar and are used similarly to other mild Allium herbs; this use is well documented in the species’ native range. As with other Allium species, ingestion can be toxic to dogs, cats and some other animals, so caution is advised where pets are present.

Allium triquetrum is not generally considered threatened in its native range but is regarded as an invasive or weedy naturalized species in parts of California and Oregon where it can form dense carpets and displace native groundcover. A notable adaptation is its three-angled scape, a reliable field character that gives the species its common name and aids identification.