I'm doing a Drabon Tales cake for a 3rd birthday party this weekend. I'm doing a stacked cake and wanted to pipe trees on the sides of the top layer. What do you think would be the best way to get a tree bark effect? Here's what I thought of so far . . .
~basket weave tip
~lots of rows with a small round tip
~pipe it as smooth as possible then add a texture

What do you think?

I made the family tree cake tree in my photos by piping rows with a number 10 (or maybe it was 12?) tip. You could use a smaller tip to make smaller trees.
The basketweave tip sounds like a good idea, too.
I think you best bet is to experiment!