Seed ball

Seed balls, also known as earth balls or nendo dango (粘土団子), consist of seeds rolled within a ball of clay and other matter to assist germination. They are then thrown into vacant lots and over fences as a form of guerilla gardening. Matter such as humus and compost are often placed around the seeds to provide microbial inoculants. Cotton-fibres or liquefied paper are sometimes added to further protect the clay ball in particularly harsh habitats. An ancient technique, it was re-discovered by Japanese natural farming pioneer Masanobu Fukuoka.

Development of technique
The technique for creating seed balls was rediscovered by Japanese natural farming pioneer Masanobu Fukuoka. The technique was also used, for instance, in ancient Egypt to repair farms after the annual spring flooding of the Nile. Masanobu Fukuoka developed his technique during the period of the Second World War, while working in a Japanese government lab as a plant scientist on the mountainous island of Shikoku. He wanted to find a technique that would increase food production without taking away from the land already allocated for traditional rice production which thrived in the volcanic rich soils of Japan.

Construction
To make a seed ball, generally about five measures of red clay by volume are combined with one measure of seeds. The balls are formed between 10 mm and 80 mm (about $1⁄2$" to 3") in diameter. After the seed balls have been formed, they must dry for 24–48 hours before use.

Seed bombing
Seed bombing is the practice of introducing vegetation to land by throwing or dropping seed balls. It is used in modern aerial seeding as a way to deter seed predation. It has also been popularized by green movements such as guerrilla gardening as a way to introduce new plants to an environment.

Guerrilla gardening
The term "seed green-aide" was first used by Liz Christy in 1973 when she started the Green Guerillas. The first seed green-aides were made from condoms filled with tomato seeds, and fertilizer. They were tossed over fences onto empty lots in New York City in order to make the neighborhoods look better. It was the start of the guerrilla gardening movement.