From the CO2Science archive: Our featured plant this week is a tree locally known in its native Australia as Sydney Blue Gum. It has green leaves, brown bark which becomes grey further up the trunk, and rose-coloured timber which is popular for flooring. No blue, apparently, which reminds us of the mystery of why Poa Pratensis is called Kentucky bluegrass when it is clearly green, not blue. Sydney Blue Gum will also not be blue when all your CO2 emissions reach it because in 2010 and 2012 there were 8 experiments showing an additional 300 ppm CO2 caused its growth to rise on average by 42.3%. By gum.