Monday 16 December 2019

Three cornered garlic - pretty but an invasive alien

Three-cornered Garlic may be seen at this time of year clothing stretches of wayside verge
Three-cornered Garlic may be seen at this time of year clothing stretches of wayside verge

Jim Hurley - Nature Trail

This is Invasive Species Week. The special event was launched in 2015 with the purpose of raising awareness of invasive non-native species, encouraging members of the public to get involved and active, and to help stop the spread of such species.

The fifth annual Invasive Species Week started yesterday, Monday 13 May, and concludes on Friday 17 May. Each day has a different theme: Monday-Freshwater and riparian; Tuesday - Urban, Wednesday - Marine; Thursday-Woodland and bogs and Friday-Small islands.

An invasive alien species that was much in evidence of late is the Three-cornered Garlic. Looking like a white Bluebell it clothed stretches of wayside verge along many roads. To some, it may have looked attractive, but it is an undesirable alien as it is so invasive that it takes almost exclusive possession of the ground it colonises, crowding our native flora and spring flowers like the Primrose and violets.

If you roll the stem of the plant between finger and thumb it is very obvious where it gets its name from: the stem is three-angled like the outer packaging of Toblerone, the Swiss chocolate bar with the distinctive triangular prism shape. Further bruising of the specimen in the hand releases the distinctive oniony and garlicy smell.

Native to western and central Mediterranean, the Three-cornered Garlic is a wild onion. It was introduced here by gardeners and when it escaped from captivity it found the Irish countryside to be a place it could thrive in. There is one limiting factor that thankfully prevents it from taking over.

Being native to the Mediterranean, the Three-cornered Garlic is not tolerant of extreme cold. To thrive, it needs mild conditions so, in Ireland, it is mainly confined to the coastal fringe that is largely frost-free. And, understandably, it is much more abundant in the Sunny South East than anywhere else in the country.

Many alien species are of little interest to our native flora and fauna. Unfortunately, the large oily seeds of Three-cornered Garlic are particularly attractive to our local ants. They collect them and spread them around aiding the plant's colonisation of fresh ground.

Being an onion, the plant also reproduces via underground bulbs. As a result, Three-cornered Garlic can form very dense colonies out-competing all other plants. All parts of the plant are edible and are safe to eat. Small infestations of the alien can be removed by repeated digging and cutting each spring.

Wexford People

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