If you've run out of clever greeting card ideas, try a card you can plant into the ground—craft blog Make and Takes has a tutorial on how to make "seed paper" and turn it into a plantable greeting card.
If you've ever made paper before, this process is not so different—you just need some paper scraps (preferably in pretty colours), a blender and some water. However, after blending the paper and water together, add some flower seeds to the mix before shaping it flat. Once it's dry, you can cut it into any shape you like and paste it on any paper or cardstock and make a greeting card.
The coolest part of this is not only is it a pretty, handmade card on its own (when was the last time someone gave you a greeting card out of paper they made?), but the receiver of the card can actually plant it in the ground and get some real flowers out of the deal. Hit the link for the full instructions.
Bloomin' Handmade Greeting Cards You Can Plant [Make and Takes]