US President Barack Obama (L) plants a tree as First Lady Michelle Obama (2nd R) Irish President Mary McAleese (3rd R) and her husband Martin McAleese (R) look on at the President’s Residence in Dublin, Ireland, on May 23, 2011. US President Barack Obama landed in Ireland on Monday for a visit celebrating his ancestral roots, kicking off a four-nation European tour. AFP PHOTO / JEWEL SAMAD (Photo credit should read JEWEL SAMAD/AFP/Getty Images)