Back in late April/early May, I took Son #3 to Story Time at our local library. The theme was "Earth Day." The librarian read three books to the children then - instead of the usual craft project - she had each child plant a single sunflower seed in a paper cup.
The seed sprouted within days and when it grew to a few inches, we transplanted it into our garden. It took a couple of months for it to grow tall and finally bloom, but check it out now.
Here's Son #3 and his prized sunflower: