The white kewra flower is called ketaki in Sanskrit.
Ketaki tree groves is part of Krnas Vrindavan pastimes
Lord Siva should not be worshiped with ketaki flowers.”
At the beginning of time in Cosmos, Vishnu and Brahma approached a huge Shiva Linga and set out to find its beginning and end. Vishnu advanced to seek the end and Brahma the beginning. Taking the form of a boar, Vishnu began digging downwards into the earth, while Brahma took the form of a swan and began flying upwards. However, neither could find his appointed destination. Vishnu, satisfied, came up to Shiva and bowed down to him as a swarupa of Brahman. Brahmā did not give up so easily. As he was going up, he saw a ketaki flower, dear to Shiva, floating down. Ketaki told Shiva that she had been placed at the top of the Shiva linga. Brahma’s ego forced him to ask the flower to bear false witness about Brahmā’s discovery of Shiva’s beginning. When Brahmā told his tale, Shiva, the all-knowing, was angered by the former’s ego. Shiva thus cursed him that no being in the three worlds will worship him. The flower of Ketaki, for bearing false witness, was cursed to be never used for the worship of Shiva.