A structural building unit, a form for making a structural building unit, and a method of forming a structure from structural building units are disclosed. A structural building unit comprising left, right, back, and front portions with the front portion extending inward and downward from the left and right front edges creates a void into which soil and plants may be placed, allowing plants to grow from any structure created with the structural building units. These structural building units are suitable for improving the aesthetic value of the structure and providing any structure built therefrom with shade and other methods of cooling, including evapotranspiration, reducing the contribution of the structure to any heat island effect. The plants also lead to improved air quality through conversion of carbon dioxide to oxygen and carbohydrates.