http://www.stamp-a-latte.com/?s=masking, loved it so copied it almost exactly as I didn't have the same stamps. It looks much better in real life. I'm going to do a few more in blue and brown tones.
I just used three scrap pieces of paper and held in place with a very small amount of double sided tape on the plain white card stock. Then using daubers I sponged SU Always Artikoke and SU Mellow Moss to a desired colour strength. I then removed the scrap paper and stamped the leaf images as desired and finished off with the birthday saying.
Products used: leaf stamps are non Stampin Up; birthday saying is from the SU Upsy Daisy stamp set; SU Always Artikoke & Mellow Moss stamp pads; white card stock.