Planting Trees; A Path to Enlightenment

Because of this, in the assemblies of the enlightened ones there have been many cases of mastering the Way bringing forth the heart of plants and trees; this is what awakening the mind for enlightenment is like. The fifth patriarch of Zen was once a pine-planting wayfarer; Rinzai worked on planting cedars and pines on Mount Obaku; and there was an old man, Ryu, on Mount To who planted pines. They all brought up the sturdiness of pine and cypress to bring out the eyes of the enlightened. This is manifesting the power to sport living eyes being opening clear eyes.

Treasury of True Teaching by Dogen Zenji

Note: Power to sport “living eyes” means to act on knowledge. “Opening clear eyes” means to enlighten self and others.