Ptichka checked out this book from the library last week. The entire tree section is fabulous. I could, if I wanted, do all the paintings. This is the one I decided to try first for a natur study deco for Caren. The process is easy. Essentially you underpaint your entire piece of watercolour paper and then draw your first tree. Then you glaze the areas surrounding the tree. Let it dry and then add a second tree. Add a wash everywhere there isn't a tree. Carry on like this until you have has many trees on your piece as you'd like.
The book uses ultramarine blue and raw sienna. I used sap green instead for this page but below are a bunch of ATCs I made with other colour schemes.
The directions in the book ask you to spatter some paint but my spattering technique isn't so hot, which is why the green ATCs have such large blotches of paint on them. I didn't make these with any particular purpose in mind so I'll probably offer them up for trade on ATCards later this week. If you're interested in trading for any of them, my e-mail address is in the sidebar. I'd prefer cards with no commercially produced images like collage sheets/stickers/etc.