Image by/from Franklyn Melville-Brown, Franklynmelvillebrown at English Wikipedia
Hydroseeding (or hydraulic mulch seeding, hydro-mulching, hydraseeding) 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.
The hydroseeding slurry is transported in a tank, either truck-mounted or trailer-mounted and sprayed over prepared ground. Helicopters have been used to cover larger areas. Aircraft application may also be used on burned wilderness areas after a fire, and in such uses may contain only soil stabilizer to avoid introducing non-native plant species. Hydroseeding is an alternative to the traditional process of broadcasting or sowing dry seed.
A study conducted along the lower Colorado River in Arizona, the United States found that hydroseeding could be used to restore riparian vegetation in cleared land. The slurry often has other ingredients including fertilizer, tackifying agents, fiber mulch, and green dye.
Originating back to the USA in the 1940s, Maurice Mandell from the Connecticut Highway Department discovered that by mixing seed and water together, the resulting mulch could be spread and sprayed over the steep and otherwise inaccessible slopes of the Connecticut expressways.
If planting a relatively large area, hydroseeding can be completed in a very short period of time. It can be very effective for hillsides and sloping lawns to help with erosion control and quick planting. Hydro seeding will typically cost less than planting with sod, but more than broadcast seeding. Results are often quick with high germination rates producing grass growth in about a week and mowing maintenance beginning around 3 to 4 weeks from the date of application. Fiber mulch accelerates the growing process by maintaining moisture around the seeds thereby increasing the rate of germination.