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Three-cornered leek - Invasive Species Information

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Three-cornered leek is a bulbous flowering plant in the genus Allium (onions and garlic) native to the Mediterranean basin. This spring-flowering bulb carries 2cm long bell-like white flowers (10-18mm) on stems which are three-sided and about 30cm high.  Along the centre of each petal is a narrow green line and between 3 and 15 flowers are arranged in a drooping one-sided umbel not unlike that of a Bluebell.

The leaves are very markedly angled, coming three to a plant from the base.  From April to June these flowers can be seen growing along roadsides, in hedges, banks and other shady places. The leaves have a distinct onion smell when crushed.

Reproduction: The seeds of Three-cornered leek are spread naturally by ants and other insects. 

Three-cornered leek - (Allium triquetrum) Flower

Three-cornered leek flower

Colour: Mid-green

Flower: White with green line on each petal

Leaf: Green with distinct angle

Stem: 3 sided

Smell: Onion / Garlic

Three-cornered leek - (Allium triquetrum) Stem
Three-cornered leek - (Allium triquetrum) flowers

How To Identify Three-cornered leek?

Three-cornered leek - Allium triquetrum

Three-cornered leek stem

Three-Cornered Leek - Allium triquetrum roots

Three-cornered leek - Allium triquetrum ID Guide

Three-cornered leek flowers

Three-cornered leek roots

Why Is Three-cornered leek A Problem?

Threatens biodiversity where the plant forms early season dense monocultural masses, particularly at protected sites.

Three-cornered leek is known to have serious impacts on the natural habitats that it invades and is very aggressive, having the potential to rapidly occupy large tracts of land.


Plants forms dense and persistent stands that totally dominate the ground-flora when conditions are suitable (moist and shaded). These stands crowd out and displace the indigenous grasses and groundcovers and can also seriously impede the regeneration of the over-storey vegetation.

What Is Three-cornered leek - (Allium triquetrum)?

Habitat: Terrestrial. Prefers damp shaded areas
Distribution in Ireland: Widely distributed in the south and south east 

Status: Established
Family name: Amaryllidaceae

Common name/s: Three-cornered garlic

European Communities (Birds and Natural Habitats) Regulations 2011 non-native invasive plant species A-Z (Updated 2017)

There are currently 35 invasive plant species listed in the European Communities (Birds and Natural Habitats) Regulations (annex 2, Part 1)...


Click on a species from the following list to find out more regarding non-native species subject to restrictions under Regulations 49 and 50.

  1. American Skunk-CabbageLysichiton americanus

  2. Brazilian Giant-RhubarbGunnera manicata

  3. Broad-Leaved RushJuncus planifolius

  4. Cape PondweedAponogeton distachyos

  5. Cord-GrassesSpartina (all species and hybrids)

  6. Curly Waterweed - Lagarosiphon major

  7. Dwarf Eel-GrassZostera japonica

  8. FanwortCabomba caroliniana

  9. Floating PennywortHydrocotyle ranunculoides

  10. Fringed Water-LilyNymphoides peltata

  11. Giant HogweedHeracleum mantegazzianum

  12. Giant KnotweedFallopia sachalinensis

  13. Giant-RhubarbGunnera tinctoria

  14. Giant SalviniaSalvinia molesta

  15. Himalayan BalsamImpatiens glandulifera

  16. Himalayan KnotweedPersicaria wallichii

  17. Hottentot-FigCarpobrotus edulis

  18. Japanese KnotweedFallopia japonica

  19. Large-Flowered WaterweedEgeria densa

  20. Mile-a-Minute WeedPersicaria perfoliata

  21. New Zealand PigmyweedCrassula helmsii

  22. Parrots FeatherMyriophyllum aquaticum

  23. Red AlgaGrateloupia doryphora

  24. RhododendronRhododendron ponticum

  25. SalmonberryRubus spectabilis

  26. Sea-Buckthorn Hippophae rhamnoides

  27. Spanish Bluebell Hyacinthoides hispanica

  28. Three-Cornered LeekAllium triquetrum

  29. WakameUndaria pinnatifida

  30. Water ChestnutTrapa natans

  31. Water FernAzolla filiculoides

  32. Water LettucePistia stratiotes

  33. Water-PrimroseLudwigia (all species)

  34. WaterweedsElodea (all species)

  35. WireweedSargassum muticum

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