The Willow Family Tree is a term used to describe a group of trees that are related to each other. The two most common members of this family are ASPEN and POPLAR, both of which have five and six letters respectively. ASPEN is a deciduous tree that is native to cold climates and is known for its white bark and yellow-green leaves. POPLAR is a fast-growing tree that is often used for timber and is known for its tall, straight trunk and broad leaves.