According to Official Guinness Records,
The tallest bloom is the Titan arum (Amorphophallus titanum), an example of which was grown by Louis Ricciardiello (USA) measuring 3.1 m (10 ft 2.25 in) tall on 18 June 2010, when it was on display at Winnipesaukee Orchids in Gilford, New Hampshire, USA.
The Titan arum, also known as the corpse flower, was measured from the tip of the bloom (spadix) to the top of the tuber.
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.