Bodhi is not only the name of the tree that the Buddha sat under when he reached enlightenment, it is the name of the state of enlightenment that he reached. The expression of Bodhi is love, compassion and wisdom and it continually shines throughout the universe like the rays of the sun. Though the most sublime essence of humankind is its Bodhi nature we are continually weighed down by our three root poisons of ignorance, greed and hatred. These emotional obscurations are like clouds in the sky and they prevent our wisdom to shine.
To cultivate a Bodhi tree we use sunlight and water. To cultivate our Bodhi nature so that we fully awaken to our Bodhi mind we apply skilful means and wisdom.
Skilful means are the various techniques that we use to bring about our enlightenment such as love, compassion, wisdom, morality, energy control and meditation. Love, compassion and wisdom counters the three root poisons of hatred, greed and ignorance. Morality protects us from generating bad karma and further ignorance. Energy control purifies the body and mind, and meditation brings us into the state of the clear light. Though the Buddha Shakyamuni taught the eighty four thousand techniques to reach enlightenment throughout the three world systems they can all be boiled down to these essential ingredients.
According to the Buddha's teachings there are three major schools and nine vehicles to enlightenment. The Hinayana school is based on the first two vehicles which are for the listeners of the doctrine, and the meditative recluses. The Mahayana school begins at the third vehicle which is based on the Bodhisattva path. A Bodhisattva's mind is intent on bringing all sentient beings to full enlightenment. The mere karmic repercussions of this type of sincerity results in supreme enlightenment. The Vajrayana school begins at the fourth vehicle of enlightenment.
The next three vehicles are known as the outer tantras which are based on purification and understanding the spiritual nature of all things. The last three vehicles are based on the three inner tantras. Mahayoga is the practice of generation and transforms everything onto the path of enlightenment. Anuyoga, the stage of perfection uses intense energy cultivation to transform the body into a Buddha mandala entering the sate of pure bliss and clarity. Atiyoga-Dzogchen-the Great Perfection. These teachings can be intellectualized gradually or suddenly realized through the direct mind to mind transmission from a realized master.
Traversing the nine vehicles of enlightenment we begin by opening the window of cultivation to let the sun shine in. When realizations begin to dawn in our mind stream we begin to feel the bliss of Bodhicitta. However, the sunlight of our own cultivation is not enough to grow a Bodhi tree. We must apply the water of compassion and social interaction to help rid the world of pain and suffering. When the Bodhi tree is used to make a boat it can rescue those lost in the ocean of samsara and deliver them to the ultimate pristine shore of Nirvana.