The Three-cornered Leek is very invasive due to the seed it produces which germinates easily to create a dense clump of leaves and flowers. In the larger garden it makes an attractive display in a woodland setting. It is a native of the Mediterranean, but is now naturalised in many parts of the British Isles, preferring shady areas, but is fairly tolerant of most conditions.
The leaves are mid-green and hairless with a keel running up one side to make them more rigid. They emerge in spring and die away after flowering. As with all Alliums it forms a bulb as an underground storage unit when the leaves die away.
The flowers appear from April to May, carried on a stalk which is triangular and gives the plant its name. They are white with a green stripe in the centre of the petals, in a one-sided umbel with between 4 to 10 to each flower head. Both male and female parts are present in each flower, and they are pollinated by Bees and insects. The black oblong seed fall mainly close to the parent plant at maturity, but can be carried further afield by nearby waterways or by ants.
All parts of the plant are edible. The leaves and flowers can be added to salads, and the bulbs can be substituted for Garlic. It is not usually mentioned as health giving, but other members of the genus are, so A. triquetrum can probably be added to the list. Care should be taken if picking as the leaves can easily be mistaken for those of many other bulbous plants which can be posionous, eg. Daffodils; the flowers are also similar to the white form of the Bluebell. The triangular flower stalk and characteristic odour are the best identifiers.
The juice of the plant is said to deter moles and moths.

Digging it up is not usually successful straight away as there are many bulblets and seeds. Over a number of years, continual cutting should eventually exhaust the bulbs and the reservoir of seeds. Any uprooted bulbs should not be added to the compost heap, and care should be taken if moving plants or soil from an infested area.
A systemic weedkiller such as Glyphosate applied in the spring, should eradicate it. A selective agent will also be effective. Re-treatment will be necessary due to the reservoir of seeds.

See also Ramsons or Wild Garlic.

Follow these links for further details on Weeds, Weed Removal and Weed Prevention.