Luke Towan makes a lot of gorgeous model railroad items, but his tutorial on making tiny trees using wire, latex, glue, and paint is especially cool to watch from start to finish.
"This tree will look fantastic on any model railroad, war gaming terrain or a display diorama and it will add life to any layout. Follow along as I step you through the process I use to create this great looking apple tree. The great part is you can still manipulate the tree to change its shape even after you've completed it. It's a time consuming process but the results are well worth the time and effort."
Check out Boulder Creek Railroad for more articles and tutorials about modeling and model railroads.