Buna (橅) is a Japanese name for Siebold's beech (Fagus crenata), a tree that grows wild mainly in high mountains. It is one of the world's largest beech forests and a UNESCO World Heritage site. Buna is also a popular bonsai material because of its whitish trunk surface and its male and female flowers that bloom in May. Buna bonsai requires careful attention to water and pruning, as it is sensitive to drought and tends to grow strongly at the top. Buna bonsai can be enjoyed year round, especially in spring for fresh greens and in autumn for colorful leaves.