Question

how to plant a container for a rooftop or balcony garden
which revision is best to make the diagram more helpful?
an illustrated list of gardening tools
a text box describing the location of the garden
a caption indicating the purpose of the diagram
a label indicating the depth of the drainage layer
bark mulch
root ball
drainage screen
drainage layer
drainage holes
now that youve blended your potting soil with one part

Explanation:

The diagram is about container - planting. Indicating the drainage layer depth is key for proper plant growth. Other options are less relevant.

Answer:

a label indicating the depth of the drainage layer