CANBERRA, AUSTRALIA - APRIL 24:  Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge watch two children help them with a tree planting as they visit the National Arboretum on April 24, 2014 in Canberra, Australia. The Duke and Duchess of Cambridge are on a three-week tour of Australia and New Zealand, the first official trip overseas with their son, Prince George of Cambridge.  (Photo by Chris Jackson/Getty Images)