This is an herb spiral, in which you plant drought hardy plants at the top and water-thirsty plants at the bottom. By adding wood, it mimics hugelkultur, in which buried wood adds nutrients and reserves water. -Grow Food Not Lawns
Designing your own vertical herb garden is a fun project. Vertical gardens allow you to grow herbs and some fruits and vegetables that do not require a lot of soil, such as strawberries or lettuce. Growing your own herbs for cooking or for medicinal.