It only flowers once in 3 years, and has the largest unbranched inflorescence (cluster of flowers) in the world. Some Titan Arums bloom every 7 or even 10 years.

"The Titan Arum grows in the Sumatran rainforest and first appears as a single tall shoot that rises like a pole out of the ground. When it is 10ft tall it branches out into three leaves.

After a year it dies down but the following season it sprouts again, and does so year after year, building up a huge tuber in the ground. Then it dies down for a longer period, the stem rots away and after a few weeks all that is left is the tuber, hidden beneath the surface of the soil. it remains like this long enough for everyone to forget the exact place where the leaves once stood.

Then, unpredictably, the tip of the spadix begins to emerge from the ground, and grows at extraordinary speed. When it is five or six feet tall the spathe is apparent, it then unfurls and spreads out like a wide trumpet – remaining like this only for a day or two. During this time it is pollinated, although no one knew how or by what."

-http://www.telegraph.co.uk/earth/3320607/David-Attenborough-a-wild-life.html