Hydroseeding (or hydraulic mulch seeding, hydro-mulching, hydraseeding) is a planting process which utilizes a slurry of seed and mulch. The slurry is transported in a tank, either truck or trailer mounted and sprayed over prepared ground in a uniform layer; helicopters may be used in cases where larger areas must be covered. Hydroseeding is an alternative to the traditional process of broadcasting or sowing dry seed. It promotes quick germination and inhibits soil erosion.
The mulch in the hydroseed mixture helps maintain the moisture level of the seed and seedlings. The slurry often has other ingredients including fertilizer, tackifying agents, green dye and other additives.

Hydroseeding is used to seed grass on commercial sites (highways/motorways etc.), lawns and areas too large, inaccessible or unsuitable for conventional methods. Starting a lawn by hydroseeding is considerably cheaper than laying sod/turf and quicker than using seed. It is also used to spread mixtures of wildflower and tree/shrub seeds or turf grasses for erosion control