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An 80-year-old American Agave that is currently growing at a rate of 5-6 inches a day inside the Matthaei Botanical Gardens Conservatory in Ann Arbor. The Matthaei Botanical Gardens Conservatory intends to remove glass panels form the roof of the conservatory to allow it grow out before it flowers this summer.

(Courtney Sacco | The Ann Arbor News )

University of Michigan’s Matthaei Botanical Gardens is preparing for the bloom of the century as its 80-year-old American agave plant nears flowering.

The American agave, often called the century plant, is a member of the asparagus family found in the southwest United States and Mexico. It is also the main ingredient in mezcal, a drink similar to tequila. While most American agave plants live to be about 20 years old, U-M’s16-foot-tall plant has been living for 80.

This particular agave was brought to the University of Michigan in 1934 after an expedition to Mexico, where it was collected from the wild. It didn’t show any sign of flowering before now, and currently, its flower stalk is growing five to six inches per day.

As the stalk grows, however, it’s getting closer to the roof of the conservatory. Michael Palmer, horticulture manager for the Matthaei Botanical Gardens and Nichols Arboretum, said they might have to take a pane of glass off the roof of the conservatory to make room for the plant’s growth.

“It’s about five feet from the glass, from the roof of the conservatory,” Palmer said. “We’re going into the warm season so the timing is perfect.”

The American agave plant has been a part of U-M’s plant collection since 1934, and the conservatory on Dixboro Road has been its home since the 1960s. Prior to that, it was held in U-M’s botanical gardens collection near Iroquois Avenue.

Although the flowering stalk is a new addition to the plant, the agave’s foliage has been growing since it was brought to the conservatory. American agave foliage is usually between three and six feet tall and six to 10 feet wide. As the plant has grown bigger over its 80-year course at the conservatory, it has become a popular plant to watch.

“We’re really excited about it. Many people have watched this plant over the years, and one of the women who works here will bring her kids every year and take a picture with it,” Palmer said.

The plant, which has leaves that are long and sharp, will eventually bloom yellow-green flowers out of small branches that shoot outward off of the flowering stalk, which resembles a large asparagus spear.

Like many agave plants the American agave is a monocarpic species. Once the plant blooms, it will die. When this happens in the wild, the plant’s identical pups that grow off the stalk make it to the ground when the plant falls over during the process of dying. The pups will then carry on the plant’s legacy and form new American agave plants.

“They’ll root and grow. It’s like the phoenix idea, where it dies, yet lives again when it comes back from the ashes,” Palmer said.

The 80-year-old agave will be cut down, but its legacy will remain through its pups, which will be kept at the conservatory.

“This plant is an original, native plant, and you don’t see that much anymore,” Palmer said. “There’s more value from plants from the wild because they have a broader genetic diversity. Science has realized that there’s more value in diversity.”

Palmer added, however, that he’s still unsure as to when the plant will actually bloom. American agave plants are usually around 20 years old with stalks between 15 and 30 feet tall when they bloom, but Palmer said that the 16-foot plant is a little different from those in the wild.

“This is a plant that is from the American southwest and Mexico, and it grows in a dry, well-drained soil and doesn’t get that much moisture in the wild,” Palmer said.

In the conservatory, the plant is kept in the desert house and watered once a week in the winter and twice a week in the summer. It is also variegated, which means it produces less chlorophyll and takes longer to produce the energy needed to grow its stalk — a rare quality to find in wild American agave plants.

“I would say anywhere from three weeks to two months will be the time when the first flower opens,” he said.

Anyone interested in seeing the American agave can visit the Matthaei Botanical Gardens on Dixboro Road in Ann Arbor. Admission is free. The conservatory is open daily from 10 a.m. to 4:30 p.m., and it stays open late on Wednesdays, until 8 p.m.

Kelly McLaughlin is an intern reporter for The Ann Arbor News. She can be reached at kelly_mclaughlin@mlive.com.