In the opening of Chapter 15, the speaker of the Gita describes the material world as an eternal Peepal tree (Ashwattha) that is uniquely "upside-down." This verse is the key to understanding the hierarchy of the 21 universes and the path to the Supreme God.
श्रीभगवानुवाच ऊर्ध्वमूलमधःशाखमश्वत्थं प्राहुरव्ययम् | छन्दांसि यस्य पर्णानि यस्तं वेद स वेदवित् || 1 ||
(ऊर्ध्वमूलम्) ऊपर को पूर्ण परमात्मा आदि पुरुष परमेश्वर रूपी जड़ वाला (अधःशाखम्) नीचे को तीनों गुण अर्थात् रजगुण ब्रह्मा, सतगुण विष्णु व तमगुण शिव रूपी शाखा वाला (अव्ययम्) अविनाशी (अश्वत्थम्) विस्तारित पीपल का वृृक्ष है, (यस्य) जिसके (छन्दांसि) जैसे वेद में छन्द है ऐसे संसार रूपी वृृक्ष के भी विभाग छोटे-छोटे हिस्से या टहनियाँ व (पर्णानि) पत्ते (प्राहुः) कहे हैं (तम्) उस संसाररूप वृक्षको (यः) जो (वेद) इसे विस्तार से जानता है (सः) वह (वेदवित्) पूर्ण ज्ञानी अर्थात् तत्वदर्शी है।
Transliteration: urdhva-mulam adhaḥ-sakham asvatthaṁ prahur avyayam chandasi yasya parṇani yas tam veda sa veda-vit
English Translation: With the roots above in the form of Purna Parmatma Aadi Purush Parmeshwar and the branches below in the form of the three gunas i.e. Rajgun-Brahma, Satgun-Vishnu and Tamgun-Shiv, it is an imperishable, extensive Pipal tree, whose divisions, small-small parts, just as there are verses in Vedas, are said to be twigs and leaves. One, who knows that tree of world in detail, is completely knowledgeable i.e. is Tatvdarshi.

This specific translation reveals that the Ashwattha tree is not merely a metaphor, but a literal map of the divine hierarchy. To understand this tree is to understand the difference between the perishable governors of this world and the eternal source of life.
The "Roots Above" refer to the Purna Parmatma (The Complete God), also known as the Aadi Purush Parmeshwar.
While the root is the Supreme God, the trunk of the tree represents Kaal Brahm (Jyoti Niranjan).
The branches spreading downwards represent the three functional deities who govern the material world:
The translation describes the small-small parts of the tree—the twigs and leaves—as being equivalent to the verses in the Vedas.
The verse concludes with a powerful statement: "One, who knows that tree of world in detail, is completely knowledgeable i.e. is Tatvdarshi."
This changes the traditional understanding of a "scholar." According to this translation:
In Verse 3 and 4 of this same chapter, it is stated that one must cut the attachment to the branches using the "Sword of Detachment" and then seek that Supreme Abode from which no one returns.
No. The speaker (Kaal) says the roots are "above" him. In Verse 17 of this chapter, he explicitly defines the Uttama Purusha (Supreme Person) as someone other than himself who enters and sustains the worlds.