Perennial ryegrass is often sold as a blend. A blend is two or more varieties of the same species of grass. Each of these are perennial ryegrasses. A mixture is two or more different species of grass mixed together. A mixture of Kentucky bluegrass and perennial ryegrass may be available at high elevation nurseries and garden centers.
Annual ryegrass is lighter in color then perennial ryegrass.
It also has a wider leaf blade, and the mid vein is not as distinct as that of perennial ryegrass. An enlarged appendage can be found on annual ryegrass where the leaf attaches to the grass shoot. It resembles large collars on a dress shirt and is called an auricle. These are easily noticed on annual ryegrass but much less so on perennial ryegrass. Annual ryegrass does not tolerate frequent close mowing.