I like the DIY toys because they are not only easy to make but also cheap. Plus when they turn out great then they are the best! So here is my DIY Trees.
I wanted to give an autumn effect so I used red, yellow and green rubber foam sheets. If you can not find those then any colourful cardboard work just fine.
I had those pins from something but I do not remember what they were originally for. So I put them to use.
I cut out some cloud-tree shapes from the foam rubber sheets and stuck them in the pins.
My son decorated his toy railway with the trees, tunnel (http://www.tinylittlebee.com/wooden-tunnel/) and houses (http://www.tinylittlebee.com/wooden-city/) 🙂