Keep in mind that none of the keyboard commands function in full screen mode as it is a limitation of Flash. This also includes naming animals, naming your island and captioning photos. You also have to click inside the game window first (that means not the white space around it). Make sure you are pressing the shift key and not the ctrl key. Make sure you are pressing and holding the Shift key while tapping the T key. Pressing them separately will not cause anything to happen.
The trees will stay invisible if you press Shift-T then click on fullscreen mode.
This shortcut makes it easy to hide animals in a forest. To harvest, press Shift-T and off you go!
|Shift-A - Shift-D - Shift-F - Shift-M - Shift-P - Shift-S - Shift-T - Shift-C - Shift-X - Shift-8 - Shift-N - Shift-Z - Shift-H - Shift-L|