Open this photo in gallery From left to right: Jen Mombourquette, Sara Spafford, and Julie Cook take a selfie in front of an agave plant in the Halifax Public Gardens on May 8, 2018. Darren Calabrese/The Globe and Mail

Spiky and with a rather prehistoric look, an American agave plant with beanstalk proportions on the verge of flowering has become an obsession in Halifax.

Four decades old, the plant will flower only once before it spreads its seeds and dies. The agave, which belongs to the historic Halifax Public Gardens, launched into an unexpected growth spurt last month, when it began to shoot up 15 centimetres a day. Once the plant had grown so tall it became entangled in the greenhouse rafters, staff moved it outside, with a special blanket and lights to add some heat, in hopes it would continue to flower despite the harsh Maritime weather.

While the plant’s daily growth slowed, its star took off on social media.

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“It’s become a celebrity,” said Margaret-Anne Bennett, who made the first posts about the agave’s flowering stalk on the Facebook page of the volunteer group Friends of the Public Gardens. She has since watched captivated locals and even tourists from visiting cruise ships flock to the plant for a glimpse.

“There’s not a minute when I can look out and not see people having their pictures taken,” said Ms. Bennett, who lives 14 storeys above the gardens and has a direct view of the agave. “I can see right now there are seven people down there. Teachers bring their classes.”

City horticulturalist Heidi Boutilier said there was much hand-wringing among gardens staff in late April over whether to put the agave outside. It is usually in the gardens’ cactus area during the warmer months and moved out of the greenhouse in May. But waiting was not an option given the sudden rapid growth.

“It was crazy,” Ms. Boutilier said. “We would come in every morning and it would be six inches taller.” The flowering stalk could grow up to 12 metres. “If it stayed in the greenhouse, we would have had to cut it down, and nobody wanted to do that,” she said. “It needed cathedral ceilings. We just couldn’t find a spot large enough before it had to go out.”

While Ms. Boutilier originally thought the agave was 25 years old, she now estimates it is likely closer to 40. There are no official records on its country of origin or who donated it to the gardens. Already the plant has outlived the average lifespan of agaves, which bloom after about 25 years.

Ms. Boutilier said it is not clear why the plant has lived so long and began to flower now, although a part of its wooden crate was cracked over the winter and some roots were exposed. She wondered if the danger to the roots triggered the effort to reproduce.

“There’s not much you can do, though, when Mother Nature is in control,” Ms. Boutilier said.

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“We are hoping that, once the weather takes off, it’ll start growing again. It is such a large plant. And it is in its final chapter. To see it in your lifetime is pretty amazing,” she said, adding: “But we’re plant geeks, right?”

It is safe to say gardens staff are not alone in their fascination. Ms. Bennett said she receives requests daily for updates on the plant’s status.

“People have become friends with it over the past 25 years,” she said. “The fact that it blooms only once in its lifetime and then … throws its seed and the mother plant dies, that’s a poignant part of the story.”

Until then, the cache on Instagram of selfies featuring the agave is likely to continue growing.

Sophia Junfang Fu, a graduate student at Mount Saint Vincent University who recently posted a picture of it, said she visits it often because its sight and smell remind her of her home in Jishou City, China.

“This plant reminded me of the warm weather back in the south of China,” she said. “And also of the vitality of life. It seems almost like a human, standing in the sunshine.”

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