The basic idea of the seed grenade is a clay container which contains seeds and a growing medium, that breaks on impact with the ground, allowing the seeds to grow. It's a fun project to do and the results can look pretty good after the plants or flowers have grown.
Step 1: What You'll Need
1) Clay working tools
2) A spoon
3) Gloves (optional but nice)
1) A ball of air hardening clay
2) A selection of seeds
4) Paint (optional)
Step 2: Making a Hollow Ball
When your ball is nice and round, start to work your thumbs into it from the top, hollowing it out as you push your fingers and thumbs in further. Squeeze the sides as you're doing this to make the walls thinner so it is easier to break after it dries.
If you find that it's too big after you've worked the clay for a while, just rip a bit off and work it again until you're satisfied.