The wand you need to help Goemoe is in the same cellar he is in.
There is a set of stairs leading up to the imp castle, which can be hard to spot (similar to the one for the warrior's guild). Approach the southern section of the castle from the east (ie circle around clockwise until you hit the section of mountain leading south) and if you still can not see the stairs along the north mountain face, just click on the mountain above (you should be able to see the gate and outer walls of the castle) and your character will find it.
The talking tree's attacks are slow, so if you stay back you should have enough time to avoid them simply by moving. Save before trying to kill the tree; there is a limited supply of tea and it is fairly easy to set off accidentally. First, you need to click on a tea barrel to open it (you may want to set it on the ground first, rather than leaving it in your inventory). Next, drag and drop it as close to the tree as possible; when an open tea barrel is dropped a poisonous cloud is produced, which will kill the tree.