This is where I have gone with my Nature Sets. With the big fern I used a Mason Stain in Hazelnut and painted it on, let it dry and then wiped to off to show the tiny details best. I then covered with a celadon glaze, and fired it.
With the tiny leaves and the big Hosta, I painted cobalt glaze on and rubbed it off, then glazed them with a light green celadon.
Pottery is a continual learning and trial and error process. Often final results are quite surprising, but none the less pleasing. I usually take a day or two, or sometimes weeks to decide how I feel about a piece. So of course when I opened the kiln, they were bluer than I hoped, but still beautiful.