Q: Do I seed below or above erosion control blankets (ECBs) or turf reinforcement mats (TRMs)?
A: Ouch! This is a trick question. There are different seeding procedures for ECBs and TRMs.
For ECBs, it is always better to seed first, then install the ECB. This puts the seed directly on the soil (where the moisture is), giving it optimal conditions for germination. The only seed that can be effectively applied over blankets would be “open” style blankets such as jute. Hydroseeding methods can be effective over some ECB only if they have moisture-holding properties. With TRM, the TRM is placed on the subgrade and then infilled with topsoil. Subsequent to the soil infill, the seed is placed and allowed to germinate. Sod is sometimes placed on the infilled TRM very effectively. Remember, the TRM provides a 3D structure for stabilization of the grass root system over time.