Find native plants in your area. Meadow flowers are probably a good place to look for cheap sources of seeds.

Mix the seeds with something that you can form into a ball. Garden soil might work well but it depends how much clay is in your soil. If it is too crumbly you could try adding clay or just use clay on its own.

Once formed into balls, yeet them to deploy! Optionally you may want to let them dry out a bit first. Could throw them, or a staff sling could be fun. I suspect it would help to make and launch them shortly before heavy rain so they get a good start with moist soil.