Sketch leaf shapes. Using the picture you chose for reference, sketch a minimum of three different leaf shape studies. You will use these shapes repeatedly in your mural. Now decide where the stems or branches will be in your mural; this will be the "bones" of your mural. A little note on composition: Foliage grows in a somewhat random patterned way. Also, keep a broad view of the whole mural as you block in the specifics.
Lightly sketch in the stems or branches of your mural. Now step back and see if you like the way your stems and branches fill the space. Adjust (without getting fussy about it).
Decide how big your leaves will be. Cut out, and tape up, colored paper leaves of different sizes and shapes to help you visualize what you are doing.
Mix at least three different shades of green paint. Using the green color paint you like, add a little white for a highlight green color. For a shadow green, mix in a little dark brown or black. Also, mix a branch color. Stems can be a similar leaf green color of the darker shade. Mix enough of each color to complete the entire mural.
Paint, stencil or stamp print the leaves. Remember that the leaves are growing out from the branches. The leaves can overlap or not, depending upon how dense you want the foliage to be. Vary the light and dark shades of the leaf color. Each leaf can be of one color, or you can paint highlights and shadows on individual leaves. But, whatever you decide, be consistent. Keep an eye on the overall rhythm of your creation.
Paint in the stems or branches. Remember, some leaves will be behind, and some of the leaves will be in front. The mural will be successful if you repeat varieties of the same thing again and again. Don't get fussy with the details. Fill the space with different variations of the same thing.