If a grass species has almost no mowing requirements (i.e., does not need to be mowed more than once or twice a year) and has no fertilizer / chemical requirements, and it requires minimal watering, the species can be treated as a groundcover. Examples of grasses that could possibly qualify as groundcovers include dune grasses and ornamental grasses. If a grass meets these qualifications, any Ks value may be chosen from Table 6 corresponding to groundcover. These values range from Ks = 0.2 to Ks = 0.7. Groundcovers with typical water needs have a Ks = 0.5. Note that choosing Ks = 0.2 implies that the species is an extremely low water user, and that there are no other regionally appropriate plants that could be installed that use less water. The species must be on a 3rd party list of drought tolerant species for the region.If the grass is mowed regularly (more than twice a year) or has fertilizer / chemical requirement, the species should be treated as a turf. The Ks range for turf in Table 6 ranges from Ks = 0.6 to Ks = 0.8. Certain species of turfgrass may use a species factor as low as Ks = 0.35 (but no lower) on the following conditions:Requirements1. A third-party resource is provided to the verification team showing that the turf will go dormant and survive without water during hot and dry conditions. This is a higher bar than demonstrating drought tolerance.2. No irrigation system is installed or planned to be installed; 3. Information is included in the occupant manual and occupant training that explains dormancy, and the fact that the turfgrass may turn brown during hot and dry conditions but additional irrigation is not needed.
Updated 10/1/13 for rating system applicability.