Butterfly Agave has broad gray leaves that form in an open rosette. The 10 to 18-inch long leaves are reflexed back near the tips with brown spines; the 1-inch long terminal spine is slightly wavy and the short marginal spines are on tubercle-like prominences. When mature a flower spike rises 10 to 20 feet with light green tipped with red. Usually flowers by about 10 years old.