Leaves of a plant called 'Bel' and the fruit 'Dhatura' are offered to Lord Shiva. The fruit with thistles is highly poisnous. Legend has it, that Shiva drank poison (because no one else - demons nor the Gods dared) when it emerged during the churning of the ocean. Reason why, Shiva is blue coloured and has a snake around his neck to keep cool the after effects of consuming poison.