The Agave is in full bloom and is being displayed at the National Trust’s Overbeck’s house and gardens, near Salcombe in Devon.
The last Agave plant to flower at the National Trust venue was eight years ago.
Unusually, the Agave mitis is also showing two spires of flowers rather than the usual single spire with both reaching 5ft in height.
It is known as a century plant because it so rarely blooms and the plants die when flowering has finished.
Many Agave plants in the UK will never bloom which makes this a rare chance for the public to see the species in all its glory.
The Agave normally has long, fleshy and spiky leaves and can take between 20 and 40 years to produce a tall flower stalk that blossoms with a number of small flowers.
The Agave mitis at Overbeck’s originates from the cool highlands of Mexico.
It thrives in the microclimate on the South Devon coast and allows gardeners to grow a range of plants from all over the world.
The subtropical gardens produce a Mediterranean feel and house many exotic plants including palms, ginger lilies and Magnolias.
Chris Groves, head gardener at Overbeck’s, said: “It’s really exciting to see this Agave in flower and for it to put on such a remarkable show.
“It is a great chance for the public to view such a rare display. The flowers will continue to open for another week before the plant begins to die back as we approach autumn.”