Hydroseeding (or hydro-mulching) is a planting process that uses a slurry of seed and mulch. It is often used as an erosion control technique on construction sites, as an alternative to the traditional process of broadcasting or sowing dry seed. With today's technology hydroseeding is the alternative to sod. There are many benefits to hydroseeding versus sod. The biggest difference being the cost. Hydroseeding cost is a fraction of the cost of installing sod.