The globe spear lily has grown to about 11 metres tall

But you had better be quick to catch the blossoming spectacle as, sadly, the Australian plant dies after flowering.

It has been a fixture in the Palm House since 1982, the same year that the 19th century building was renovated.

Palm House gardener Philip Doherty said he first noticed flowers on the plant a few months ago.

"It took us all by shock because we had always wondered when it was going to flower," he said.

"The plant is monocarpic, which means it dies after flowering - we will just have to try and get seeds off the flower head once it finishes blossoming."

A common sight in eastern Australia, Belfast's version stands much taller than the version down under at about 11 metres.

"It doesn't grow that tall out in the wild, only about two metres," he said.

The plant is tied at the top to keep it growing straight

"It could be the conditions in here, plus it's in a pot so the energy has to go somewhere - if it doesn't go into the foliage it will go into the flower. It is quite unique."

Although the crimson flowers have been most welcome, the changes to the plant mean it is no use any more for exhibiting in other gardens.

"The leaves used to fan out in a circle, with each leaf about two metres long - it was quite attractive, but now it's flowering, we're not going to be able to use it again which is a pity," he said.

"That's the law of the jungle - there's no arguing with nature."

However, the Palm House gardener remains proud of his blooming charge.

"It's quite unique for Belfast - it's a sort of Jack and the Beanstalk fairytale," he said.

The Palm House is one of the earliest examples of a glasshouse constructed of curved iron and glass, older than its more famous counterpart at Kew.

The plant still has some foliage but not as much as it used to

Built in 1840 with the central dome added 12 years later, the temperature inside and its tropical displays change with the seasons.

Some accounts suggest that the Botanic Gardens attracted up to 10,000 people on Saturday afternoons in Victorian times.

Many of the species displayed in the 19th century are still grown today.

Staff at the Palm House certainly hope they will be able to germinate another Globe Spear Lily once this one finally expires.

With free admission, horticulture enthusiasts had better act quickly to see it, as there may be another 23-year wait.