A fertilizer tree is a type of tree that is specially made to help nourish other plants and make them grow bigger and healthier. They work in a similar way to how people use fertilizer to make their garden plants grow: by providing them with the nutrients they need to stay healthy. Fertilizer trees are planted near other plants and when the leaves of the tree fall off, they drop these nutrients onto the soil below and provide the other plants with the extra nourishment they need. This helps the other plants to grow better and quicker!