Board Thread:Help Desk/@comment-24094483-20131026063837

Can't get saplings to progress into trees. Well, more accurately, I can't get specific saplings to grow while others will. Here's an image of my terrarium (teehee)

http://imgur.com/raE6yYu

The inner two trees grew with no problems, and I put the walls in behind them afterwards. The outer trees have 5-7 grass blocks under them, no ceiling (last ditch attempt to get them to grow), and no wall nearby.  