Irish Spurge

Irish Spurge in Church Path?

Photo 10 Sept 2019

 

This odd, primitive-looking plant appeared under the brambles in Church Path.  Its flowers had no petals, just yellow-green bracts.  Each flower contained a tiny green ball, like a pumpkin on a stalk - with warts.  These grew like a time capsule, bursting open to eject three seeds.  


It was Irish Spurge.  Plant records say this is found in North Cornwall, North Devon and North Somerset, in South Ireland and - the Pyrenees - not in Malden.  The Vascular Plant Red Data List (IUCN, 2001) classifies Irish Spurge as “Vulnerable” in England.

Seeds of Irish Spurge have also been found in rocks laid down before 21 thousand years ago, in sediments deposited by rivers.  Seeds like these are studied to help date fossils and to make maps of the climates of continents in different archaeological eras.  Significant research on Irish Spurge seeds was published in 2015 comparing the genes of the separate populations.

Temperatures before 21,000 years ago (The Last Glacial Maximum) became so low that the ice sheet covered half of England and all of Ireland.  Seeds ceased to be deposited.  Temperatures then rose, and sea levels with them.  The Irish Sea cut Ireland off from England, then the English Channel cut off the British Isles from Europe. 

 

The oddly separate locations in which Irish Spurge is found today are surprisingly similar to the places where its seeds were found in rock sediments deposited before the Ice Age.  Google helped to fund scientists to make a detailed comparison of the genetic structure of Irish Spurge in its different locations.  The report (published by the Linnean Society in 2015) found that the plants in Ireland today appeared to have descended from the English stock, and those in England from Spanish/French stock.                                                                                            

 

This implied they crossed the sea and re-colonised the same separated pockets of land.  How could they cross the Channel, then the Irish sea?  Why ever did they only re-colonise the same small pockets of land they were first recorded in over 21 thousand years ago?  Are these places really the only habitats and climates that suit Irish Spurge?  Is today’s climate in those places really so perfectly the same as it was before the Ice Age?  Detailed climate maps suggested this might largely be correct.

But whatever is this pre-historic rarity doing in our Church Path?  What a reminder to be ultra vigilant about every seedling that appears in this part of Kingston’s Conservation Area - where bricks and gravel have been steamrollered  into ancient wildflower meadow.

Irish Spurge (Euphorbia hyberna)