Ryegrasses are cataloged into 4 categories.

Annuals 6 to 8 months
Italians 6 to 15 months
Intermediates 2 to 3 years
Perennials 3 to 5 years

Ryegrasses are high energy, easily digestible grasses that are best suited for grazing or high moisture harvest. Ryegrass is designated as being either a diploid or a tetraploid. Diploids have half the  chromosomes as a tetraploid does. Tetraploids retain more moisture, the leaves are shinier, and typically grow faster than diploids. Diploids normally are hardier plants, slower in production, and have a longer lifespan than tetraploids.