The thing that would have helped you most was just to ask how to set up a 2x3 tile large tree so you can tile it ;3 You know, it's about getting a single fish or learning how to fish, and in this case the only graphic skill you need is copy and paste.
In such cases it is also extremly valuable to see what your result was. People cannot tell you where you went wrong, if they don't see what happend!
I have some vague ideas, but I could not replicate any issue^^'
Because, if I simply copy and paste my own tree like this:
it tiles beautifully horizontally:
and vertically...
...it nearly works perfectly, the only issue being that I need a special part for the sides or - we talk about MZ after all - simply map the lower part of the trees on a layer below.
Either, of our tree construct, we need to map the red row on a lower layer and the turquoise on top or we simply set them up as premade tiles:
Done. This can be done in any graphic program that supports transparency and locked grids in just a few minutes. There might be more "edge cases" (haha, you know, because they affect the edges...), but they should all be solvable by utilising the layers and/or a similar edit like I did here for the critical row.
You might need to think a little and practise until you understand how to solve all cases (like here, for mapping a 4 tree high field I needed a second to figure which parts to use)
