1973 Flyer for seed bombs
URL: http://www.lizchristygarden.org/lcbh_files/seed_bomb.html

Seed balls are simply seeds mixed with equal proportions of dried compost and clay, formed into small balls, and dried for later sowing.

To make them, simply select the seeds to be used - thick-skinned seeds will need to be scarified, and some seeds need heat or cold to bring them out of dormancy. Legumes will require inoculant if they are to fix nitrogen. Also, for species that can benefit from mycorrhizal relationships, adding the spores of mycorrhizal fungi such as the genus Glomus and/or Rhizopogon, species Gigaspora margarita, and/or Pisolithus tinctorus would be beneficial. [This list is not exhaustive, but these are readily available through Fungi Perfecti.]

Mix one part seeds with one part dry compost.

Next, add one part dry clay and mix.

Then spray in water a little at a time and mix it together until you have just enough water to hold everything together without crumbling.

After that, form the mixture into balls 2~3 cm in diameter.

Finally, dry the balls for later use.

Once dried, the balls are ready to be spread over land that you want to plant. When the rains come, the seeds will germinate.

http://groovygreen.com/groove/?p=714

Also check out "Guerrilla Gardening:"
http://www.guerrillagardening.org/