Three years ago I used erosion control blankets to keep dirt in place while my grass seed could grow (which it did with only a little success). The label said that the mat would degrade. Nope. The string used to hold the straw together is still there after three years. The freeze killed most of the St Augustine grass (yay!), and I am raking and thatching the front yard to seed with a buffalo grass mix (which is native to the area). Between pulling up the St Aug runners and the embedded strings, raking is slow going. Live and learn.