Allium triquetrum

Allium triquetrum (Amaryllidaceae), three-cornered leek, is native to the Mediterranean region and has become widely naturalised elsewhere, sometimes invasively. Its distinctly triangular flower stem, 15 to 45 cm tall, bears a nodding spring umbel (March–May) of white, green-striped bells reminiscent of lily-of-the-valley. It favours cool, shaded spots. Grow in cool, well-drained soil, in shade to part shade; keep an eye on it, as it self-seeds freely.