That's the hydro mulch and it performs these 3 valuable functions. Seeds are kept moist because hydro mulch retains 10-15 times its weight in water.
Water is the key ingredient for a quicker, thicker lawn.
Wind and water erosion can prevent satisfactory results. Hydro mulch helps maintain soil temperature and protects young seeds from the scorching sun. It forms an almost perfect micro-climate for maximum germination. As your lawn becomes established, the hydro mulch will gradually decompose and disappear. Hydroseeding provides an instant green carpet which eliminates all dust and mud problems and allows limited foot traffic the same day it is installed.