Allium triquetrum L. (W Medit.) – A rare, locally naturalized escape from cultivation or established throw-out. First documented from woodland in Stekene (Steengelaag) where a small population persists since 2013. In 2017 also found in a grassy bank (former railway track) near Brugge. In the latter locality A. triquetrum grows along with congeneric species like A. pendulinum and A. roseum.
Allium triquetrum is similar to A. pendulinum but its flowers are much larger and not stellate. It also is a taller, more vigorous species. A. paradoxum, another species with triquetrous stems, differs in having inflorescences that consist entirely or mostly of bulbils (vs. of flowers only in A. triquetrum and A. pendulinum).
Selected literature:
Badr A. & Elkington T.T. (1978) Numerical taxonomy of species in Allium subgenus Molium. New Phytol. 81: 401-417. [available online at: https://www.researchgate.net/publication/230898597_NUMERICAL_TAXONOMY_OF...
Cela Renzoni G. & Garbari F. (1970) Il genere Allium L. in Italia: I. Allium pendulinum Ten. et A. triquetrum L. G. Bot. Ital. 104: 61-73.
Fitter R.S.R. & Stelfox A.W. (1964) Allium triquetrum L. in Ireland. Irish Naturalists' J. 14: 316.
Garcia C.C., Nepi M. & Pacini E. (2006) Structural aspects and ecophysiology of anther opening in Allium triquetrum. Ann. Bot. 97: 521-527.
McMillan N.F. (1965) The garlic, Allium triquetrum L. in Ireland. Irish Naturalists' J. 15: 21.
McMillan N.F. (1968) Allium triquetrum L. and Oxalis articulata Savigny in Co. Wexford. Irish Naturalists' J. 16: 26.
Murphy R.J. (1987) Triquetrous leek (Allium triquetrum). Botanical Cornwall Newsl. 1: 5-6.
Nordenstam B. (1978) On the typification of Allium triquetrum L. Taxon 27(4): 371-373.
Nutt R.D. (1967) A note on Allium triquetrum. Bull. Alpine Gard. Soc. Gr. Brit. 35: 59.