Genus Alnus is a group of plants commonly known as alders. There are several synonyms that refer to this genus, including Alnaster, Alnobetula, Alnus subg. Clethropsis, and Clethropsis. These plants are found in several parts of the world, and they are prized for their ability to fix nitrogen in the soil. The alders are also known for their contribution to the ecosystem, providing habitat and food for a wide range of animals. They are deciduous trees or shrubs with simple leaves, and they are often used for ornamental purposes in gardens and parks. Despite the numerous synonyms that exist for the genus alder, the plant remains a highly important and recognizable species.