This engaging, science-packed picture book follows two very different groups of young friends as they each plant a tree and then share their excitement through a series of pen pal letters. In the USA, five friends plant an acorn that grows into an oak tree seedling. They learn about their tree's life cycle and how it will become an ecosystem that gives food and a home to birds, insects, and other animals. In Senegal, Africa, five friends plant an acacia tree as part of Africa's Great Green Wall Project. They learn how their tree will nourish the soil, trap water, shade the hot land, and help their village grow crops. Both groups of friends also discover that their trees will help fight climate change!