Once the patches are removed or killed, you can seed or sod these spots. Many bunch-type grass weeds, such as crabgrass, can show up as thick clumps. Crabgrass is yellowish-green and usually shows ...

and it has to do with the fact that it is made with only one species of grass: "Perennial ryegrass is what is considered a 'bunch' type grass, meaning that it grows by forming clumps or large ...