A massive plant that can be used to make a popular Mexican liquor surprised horticulturists at the Halifax Public Gardens recently by shooting out a flowering stalk that quickly made it too large to fit inside the greenhouse.

One of the Public Gardens' Agave americana, commonly known as the century plant, sent out its reproductive stalk — or mast — last week and continues to grow at a staggering rate of more than 15 centimetres a day.

"She wasn't waiting for anything," said horticulturist Heidi Boutilier, who looks after the plants in the 6.5-hectare downtown park.

"It would have been nice if she would have done this in a couple of weeks when the weather was a little nicer but the mother plant itself will withstand temperatures in the single digits."

The plant's mast looks a lot like a massive asparagus spear. (Cassie Williams/CBC)

Boutilier said she's not sure how the "fridge-like" temperatures will affect the flowering part of the plant, which looks strikingly like a 1.5-metre-long asparagus spear at the moment.

Once the mast reaches its full height of six to 12 metres, Boutilier said the flower will look more like a coniferous tree.

"The multiple stems that come off of this mast … have multiple flowers on them in clusters. It's technically called an florescence," she said.

The fully developed flowers of the agave resemble coniferous trees. (Alvesgaspar/Wikipedia)

The plants are native to arid climates like parts of Mexico and usually live about 30 years. On average the plants bloom at about 25 years and then, with their reproductive duty complete, they die.

The sugary nectar of the massive, blue-green plant is used as both a sweetener and to make mezcal, a tequila-like liquor common in Mexico.

"This stem, the mast that grows the flowers, itself is cut, and the liquid that comes out of that — which I've read can be 1,000 litres … [produces] mezcal," said Boutilier.

The massive agave had been housed in one of the Public Gardens greenhouses until its flowering mast became too large for the building. (Cassie Williams/CBC)

She said she's not sure where the name century plant comes from.

"I'm not sure how it got that common name. It doesn't live to be a century, although some plants I know have lived ... to be 80 years old before they've flowered," she said.

The massive plant — including its root ball — weighs more than 450 kilograms and requires heavy machinery to move to and from the greenhouse where it spends the winter.

Boutilier says it's not clear what effect the "fridge-like" temperatures in Halifax will have on the plants flowering mast. (Cassie Williams/CBC)

There are several agaves of various sizes in the Public Gardens greenhouse. Boutilier said this is the first time she's seen one of them bloom.

"Some of our gardeners that have been with us for 20, 30 — we have one gardener who has been here 40 years — they witnessed one other agave that we had do the same thing and that would have been, I think, 15 years ago."

Boutilier said she's excited to find out how the bloom smells.

The plant is in the process of being planted in the cactus and succulent garden of the Public Gardens, located between the main gate and the goose compound. (Cassie Williams/CBC)

The public are encouraged to visit the agave, which is being planted in the cactus and succulent garden of the Public Gardens, located between the main gate and the goose compound.

"We're all pretty excited about this but we're all plant geeks, so — but we would love anybody's comments or questions about it," said Boutilier.