Mahabharata Anushasna Parva Chapter 98:2

Mahabharata Anushasna Parva (Dana Dharma Parva) Chapter 98:2 That is Poison which tortures the mind exceedingly by its odour. Know again that Amrita is highly auspicious and that Poison is highly inauspicious. All the (deciduous) herbs are Amrita. Poison is born of the energy of fire. Flowers gladden the mind and confer prosperity. Hence, men of righteous deeds bestowed the name Sumanas on them. That man who in a state of purity offers flowers into the deities finds that the deities become gratified with him, and as the consequence of such gratification bestow prosperity upon him. O ruler of the Daityas, those deities unto whom worshippers offer flowers, O lord, uttering their names the while, become gratified with the offers in consequence of their devotion. The (deciduous) herbs are of diverse kinds and possess diverse kinds of energy. They should be classed as fierce, mild, and powerful. Listen to me as I tell thee which trees are useful for purposes of sacrifice and which are not so. Hear also what garlands are acceptable to Asuras, and what are beneficial when offered to the deities. I shall also set forth in their due order what garlands are agreeable to the Rakshasas, what to the Uragas, what to the Yakshas, what to human beings, and what to the Pitris, in proper order. Flowers are of diverse kinds. Some are wild; some are from trees that grew in the midst of human habitations; some belong to trees that never grow unless planted on well-tilled soil; some are from trees growing on mountains; some are from trees that are not prickly; and some from trees that are prickly. Fragrance, beauty of form, and taste also may offer grounds of classification. The scent that flowers yield is of two kinds, agreeable and disagreeable. Those flowers that emit agreeable scent should be offered to the deities. The flowers of trees that are destitute of thorns are generally white in hue. Such flowers are always acceptable to the deities, O lord! One possessed of wisdom should offer garlands of aquatic flowers, such as the lotus and the like, unto the Gandharvas and Nagas and Yakshas. Such plants and herbs as produce red flowers, as are possessed of keen scent, and as are prickly, have been laid down in the Atharvana as fit for all acts of incantation for injuring foes. Such flowers as are possessed of keen energy, as are painful to the touch, as grow on trees and plants having thorns, and as are either bloody-red or black, should be offered to (evil) spirits and unearthly beings. Such flowers as gladden the mind and heart, as are very agreeable when pressed, and as are of beautiful form, have been said, O lord, to be worthy of being offered to human beings. Such flowers as grow on cemeteries and crematoria, or in places dedicated to the deities, should not be brought and used for marriage and other rites having growth and prosperity for their object, or for acts of dalliance and pleasure in secrecy. Such flowers as are born on mountains and in vales, and as are agreeable in scent and aspect, should be offered unto the deities.