First flower I tried was a Peony, this Peony tree has sentimental value to me and I wanted to preserve its one flower a year if I am lucky. I totally covered the flower with the silica gell when it was in its prime. I left it alone without opening the airtight container for two weeks. When the two weeks were up (in my diary) I was exited to open the container.. The results were stunning, its kept its beautiful pink colour, shape, now I have a flower forever as a memory to my younger sister.
Give it a go....