http://heavypetal.ca/archives/2007/03/how-to-make-seedballs/
"This past weekend, Al from my guerilla gardening group led a seedball-making workshop. I loved it; it was so satisfying just to get my hands muddy and spend a couple hours in a zen-like trance rolling seedballs… I highly recommend the process!
Here’s the recipe:
5 parts dry red clay*
1 - 2 parts water
1 part seed**
3 parts dry organic compost
We used a 16oz. plastic cup as a measure, which made enough for approximately 300 seedballs. After mixing together all the dry ingredients, we added enough water to form a mix that held together without crumbling but wasn’t so wet that it wouldn’t roll into balls. Pinching off small bits of the lovely mud, we rolled penny-sized balls and set them in trays. They will sit on my windowsill for three or four days until completely dry."
Read the entire story at Heavy Petal.