How about a doing a birthday cake in a tree theme. I did this for my daughters 1st birthday. I admit, I'm the one who loves trees, but I also designed her room with a tree theme, so it seemed like a good idea. :)
I decided to go with 2 different sized cupcakes for those at the party who might want to control the portions, or for any little kids who couldn't handle an entire cupcake. It ended up adding to the overall design, which was an added bonus.
As for the decoration, you'll see in the picture, I started with chocolate cake for the cupcakes. For icing I used 2 different shades of green to add to the detail of the leaf part of the tree. Chocolate frosting for brown trunk and branches. I just went over top of the already frosted green cupcakes for the branches. Then I used a lighter brown color for some lines in the trunk for detail. I also used some lighter shade green to make grass at the bottom of the tree.
Finding a circular platter to put it on was "the icing on the cake" (hahaha, sorry for the bad pun) because I find it framed the whole thing well.
Overall, it was pretty easy to make, and turned out really nice, at least I think so. So now you can make a tree birthday cake too (or any occasion you might need it for)