Srimad Bhagavat Gita commentary chapter 15 verse 1

 Chapter 15 verse 1 

“The Supreme Divine Personality said: They speak of an eternal aśhvattha tree with its roots above and branches below. Its leaves are the Vedic hymns, and one who knows the secret of this tree is the knower of the Vedas.” 

I am not sure if I have understood completely the import of this sloka. A quick google search indicates that the reference to the upside down Ashvatta tree (sacred peepul tree in India) has been referenced in sanatana dharma scriptures in bhagavat gita, Srimad Bhagavatam, Katho Upanishad and other parts of Vedas as well. It has also found in norse and Scandinavian lore. A normal tree takes roots from the ground, grows braches, leaves and sprouts out to the sky. The root could be construed as taking foundation in material nature of the world and branching out in the material world due to the reflections of the 3 gunas. The leaves which indicate whether the tree is alive and well or not is the nourishment of the Vedas which sustain both material and spiritual life on earth. This description of a upright tree would represent the jivatma and how it operates in this material world. However if you reverse the tree into an upside down ashvattha tree, then the roots of the tree comes from the divine in the metaphorical, infinite sky and space- supreme consciousness. The branches and growth of the branches up and down are the myriad lives jivatmas tend to live going through the grind of cycles of birth and death impacted by the interaction of the 3 gunas and the material world. The knower of the upside down tree knows the essence of Vedas per Bhagwan.