A single rye plant can grow up to 2 feet tall in as little as two months, depending on your climate and how often you mow your lawn. It may take three months for your rye grass to reach full growth if you do not fertilize it regularly. Rye grass spreads through underground stems called rhizomes, so if you want to have rye grass in multiple areas of your yard, you may need to plant multiple rhizomes in different areas of your yard. Rye grass grows best in cool weather and does not like extreme heat or cold. If you live in an area with cool temperatures year-round, planting rye grass may not be an issue for you. If you live in an area with warm temperatures year-round, planting rye grass may not be an option for you. You can find out how cold your climate gets by using this cool weather grass calculator: https://www.rhs.org/uk/learning/landscaping-