adhas cordhvam prasrtas tasya sakha
adhas ca mulany anusantatani
The branches of this tree extend downward and upward, nourished by the three modes of material nature. The twigs are the objects of the senses. This tree also has roots going down, and these are bound to the fruitive actions of human society.
Commentary by Srila Prabhupada
The description of the banyan tree is further explained here. Its branches spread in all directions. In the lower parts, there are variegated manifestations of living entities—human beings, animals, horses, cows, dogs, cats, etc. These are situated on the lower parts of the branches, whereas on the upper parts are higher forms of living entities: the demigods, Gandharvas and many other higher species of life. As a tree is nourished by water, so this tree is nourished by the three modes of material nature. Sometimes we find that a tract of land is barren for want of sufficient water, and sometimes a tract is very green; similarly, where particular modes of material nature are proportionately greater in quantity, the different species of life are manifested accordingly.
The twigs of the tree are considered to be the sense objects. By development of the different modes of nature we develop different senses, and by the senses we enjoy different varieties of sense objects. The tips of the branches are the senses—the ears, nose, eyes, etc.—which are attached to the enjoyment of different sense objects. The twigs are sound, form, touch, and so on—the sense objects. The subsidiary roots are attachments and aversions, which are byproducts of different varieties of suffering and sense enjoyment. The tendencies toward piety and impiety are considered to develop from these secondary roots, which spread in all directions. The real root is from Brahmaloka, and the other roots are in the human planetary systems. After one enjoys the results of virtuous activities in the upper planetary systems, he comes down to this earth and renews his karma, or fruitive activities for promotion. This planet of human beings is considered the field of activities.
Commentary by Sri Visvanatha Cakravarti Thakur
The branches of this tree spread down (adhah) in the form of animals and others, and upward in the form of the birth of devatas and other elevated beings. These branches increase and increase by the watering, in the form of actions of the three gunas (guna pravrddha). The small twigs of the branches are the sense objects such as sound (visaya pravalah). Moreover, it can be inferred that, at the base of the tree, unknown to all people, is some great treasure. There are external roots from the branches of the asvattha, meaning in this case banyan tree, which is dependent for support on both the main root and the external roots. These secondary roots, the cause of continued action, spread out everywhere (anusantantani) below Brahmaloka (adhah), in the planet of humans. Karma anubandhini means that after enjoying the results of ones actions, those actions become stimulus for actions in another human birth.