Alders are deciduous trees or shrubs belonging to the genus Alnus. They are commonly found in temperate regions and thrive in wet, lowland areas. Alders are known for their distinctive catkins, which are cylindrical flower clusters that appear in early spring. These trees can grow up to 100 feet tall and have a lifespan of around 60 to 100 years. One notable feature of alders is their ability to fix nitrogen in the soil, thanks to a symbiotic relationship with certain bacteria. This makes them important for improving soil fertility. Alders are also valuable for wildlife, providing habitat and food for various species, including birds and insects.