What should not be offered to Śiva?

tradition commonly avoids ketakī flowers, tulasī, and in many homes kuṅkuma and turmeric on the liṅga; customs differ, so follow your family.

Śiva is the ascetic of Kailāsa, and his worship favours simple, cooling things: water, milk, bilva, dhatūrā, white flowers, bhasma and sandal. A few items are traditionally kept away. The ketakī (screw-pine) flower is the best known. Tulasī is reserved for Viṣṇu. Many Śaiva homes do not apply kuṅkuma or turmeric on the liṅga itself — which are seen as marks of auspicious married life and of the Devī — though they may be offered to Pārvatī beside him.

Some also avoid offering water from a conch (śaṅkha) to Śiva, based on a Purāṇic story. In parts of India, though, customs differ, and some temples do use turmeric or kuṅkuma.

None of these is a cause for fear. If something was offered by mistake, gently remove it, offer water and a bilva leaf, and say a short prayer.

Tradition says that when Brahmā and Viṣṇu searched for the ends of an endless pillar of light, Brahmā falsely claimed he had reached the top, with the ketakī flower as his witness. Śiva set aside the ketakī from his worship for that false testimony.

Source: Śiva Purāṇa (ketakī story) · Dear to Śiva: bilva, dhatūrā, water, bhasma

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