For 20 years the plant has been almost invisible in the Cambridge University Botanic Garden.
But now the Titan Arum, one of the largest flowers, is set to become the centre of attention.
The giant bloom is expected to emerge for the first time next week, giving visitors a brief opportunity to see one of the most extraordinary plants on earth in its full glory.
Previous flowers at Kew and Edinburgh drew vast crowds.
Rob Brett, the glasshouse supervisor, said no one knew who planted the Titan Arum, which was brought into the tropical palm house five years ago.
The plant has since thrown up a succession of 2.5m long leaves, each one standing alone for between six and 18 months before falling dormant.
Last Monday, staff noticed something strange about its latest shoot. "It took us by surprise but by Wednesday we were sure it was a flower," Mr Brett said.
The central, spike-like spadix has grown 8cm a day since then and should open into a 1.8m crimson flower between Tuesday and Thursday next week.
It will also emit a corpse-like stench that attracts the insects that pollinate it in its native Indonesia.
The garden will stay open late on the day the Titan Arum flowers as the bloom will have faded within a week.
A webcam has been set up to monitor the flower's progress: www.botanic.cam.ac.uk/webcam2.htm