They have dedicated their lives to the welfare of others. They are the perfect example of noble life.
One may take excellent lessons from the pious trees, who offer innumerable benefits, such as fruits, flowers, cooling shade and medicinal extracts. Even when a tree is suddenly cut down and dragged away, the tree does not protest but continues to give service to others in the form of firewood. Thus, one should become the disciple of such magnanimous trees and learn from them the qualities of saintly conduct. (Srimad Bhagavatam)
Taking shelter of the shade of the trees, Kṛṣṇa became very happy. While walking He began to address the inhabitants of Vṛndāvana. “My dear Stokakṛṣṇa, My dear Varūthapa, My dear Bhadrasena, My dear Sudāmā, My dear Subala, My dear Arjuna, My dear Viśāla, My dear Ṛṣabha–just look at these most fortunate trees of Vṛndāvana. They have dedicated their lives to the welfare of others. Individually they are tolerating all kinds of natural disturbances, such as hurricanes, torrents of rain, scorching heat and piercing cold, but they are very careful to relieve our fatigues and give us shelter. My dear friends, I think they are glorified in this birth as trees. They are so careful to give shelter to others that they are like noble, highly elevated charitable men who never deny charity to one who approaches them. No one is denied shelter by these trees. They supply various kinds of facilities to human society, such as leaves, flowers, fruit, shade, roots, bark, flavor extracts and fuel. They are the perfect example of noble life. They are like a noble person who has sacrificed everything possible–his body, mind, activities, intelligence and words–in engaging in the welfare of all living entities.”
The Hare Krishna Movement 