Background information and definitions
Seed balls are made of a mixture of soil and seed. These balls can be planted, thrown or scattered over wide areas from aircraft. Use of the seed balls may reduce seed predation and desiccation, thereby increasing germination of the seeds in seed balls.
Supporting evidence from individual studies
A randomized, replicated, controlled study in three blackbrush shrubland sites in California, USA (Jones et al. 2014) found that planting seed balls containing shrubland species resulted in lower seedling numbers than sowing seeds. Seedling emergence was lower in areas where seed balls containing shrubland species were planted (0–5% of seeds) than in areas where seeds were sown (17–22% of seed). Plots measuring 70 cm x 70 cm were established and in January 2010 seed balls planted in some plots and seeds sown in the other plots (number of plots unclear). Seedling emergence was assessed in between March 2010 and May 2012.Study and other actions tested