Ketaki Flower is not offered to Lord Shiva and other Gods in Hindu Religion
The Ketaki flower is highly fragrant and is used extensively for perfumes and aromatic oils. But the Ketaki flower is prohibited from being used as an offering in religious rituals.
Why is the Ketaki flower not used in Worship?
Once Lord Brahma and Lord Vishnu had an argument about who was more supreme. The argument escalated and both of them got ready for battle.
Both the Gods decided to fight. Vishnu in great fury discharged the Mahesvara weapon over Brahma. Brahma retaliated and aimed the Pasupata weapon at the chest of Vishnu. If both these weapons had collided, it would have caused havoc on creation. Thus Shiva appeared as a pillar of light in between both the weapons and absorbed them.
The story is mentioned in the Shiv Puran and also explains the significance of Shiv Ling.
Both Brahma and Vishnu were distracted by this pillar of light that extended vertically and seemed endless. They stopped fighting and decided to inquire into the nature of this mysterious column of fire. Vishnu assumed the form of a boar and went in search of the root. Brahma took the form of a swan and went up in search of the top. Both of them travelled a great distance but could not reach the either end of the pillar.
Vishnu returned and admitted to Shiva that he could not find the end of the pillar. Brahma on his way up found a ketaki flower and convinced it to be a witness to the lie that Brahma had discovered the top of the pillar. Upon his return, Brahma cited the ketaki flower as a witness and told Shiva that he had found the end of the pillar of light.
Shiva immediately found out about the lie and became enraged at the ketaki flower. He cursed Brahma of not being worshipped on earth. He also cursed the ketaki flower that it would stop being used in any Hindu worshiping rituals.
This story is mentioned in Shiva Puran and hence people have stopped using the ketaki flower in relgious rituals and festivals.
The story also accurately predicts the decline of Lord Brahma worship and the absence of prominent temples dedicated to Lord Brahma.
The most famous temple dedicated to Lord Brahma is located at Jagatpita Brahma Mandir in Pushkar, Rajasthan