I'm sure they serve a purpose. .I got a dozen of them. All I know is I used a crystal (I thought it was fire) on Grain Seeds, and harvested them as soon as Moogle told me that I could.
However they were worthless.. sold at the AH for less than 200 if I remember correctly. .
I'm looking for somewhere to learn to Garden .. haven't found it here. anyone able to give me direction please post.