Rising from the moist soil like an alien pod, a rare plant affectionately known as Morticia has been giving many Franklin Park Zoo visitors reason to hold their breath.
Horticultural gawkers may soon be holding their noses, too.
Since Friday, the 4-foot-6-inch amorphophallus titanum, better known as the corpse flower, has been on the precipice of blooming, which occurs once every 5 to 15 years.
When it finally unfurls, which zoo officials say will be any moment now, the flower will emit an odor of rotting flesh, an evolutionary advantage that draws flies, beetles, and other pollinators that help it reproduce. The bloom could reach 5 feet wide.
“I’m excited,” said Mitch Rosenfield, 40, of Roslindale, one of about 250 people who toured a tiny, temporary greenhouse set up near the zoo’s entrance Sunday morning. “The suspense is killing me.”
Weighing in at 200 pounds and requiring a forklift to move it, the massive potted specimen is one of five at the zoo that were donated by a New Hampshire doctor, but is the only one in a flowering phase.
Zoo staff said that as of 8 p.m. Sunday, more than 6,700 people have pushed through the plastic curtains into the greenhouse to view the plant, native to Indonesia.
And in a nod to plant geeks and the horticulturally curious, the zoo opened early Sunday and offered free admission to see Morticia, at whose image dozens of cameras snapped, fingers pointed, and children’s mouths hung agape at the plant’s slow lurch toward reproduction.
To better view the flower, zoo staff hung a large, angled mirror above Morticia, which had begun opening to reveal a corona of deep lavender.
A sheath of protective leaves has begun to fall away, exposing the massive, striated underside of the petal-like surface, called a spathe, that clings to the oblong, vertical core, known as the spadix.
To Anna Cynar, 26, a science teacher in Fitchburg, the true wonder was that such a low-intensity spectacle would draw so much interest.
“It’s nice to see faith in the natural world, that people would leave their homes and their computers to see a plant bloom,” Cynar said.
Harry Liggett, 46, manager of horticulture and grounds at the zoo, has been responsible for the care of Morticia and a similarly sized corpse flower that the zoo staff named Fester, in addition to three smaller versions.
Fester, the first to bloom, unleashed its torrent of odor one night last week, catching zoo staff by surprise.
“A security guard came in to change a propane tank, said it smelled god-awful, and left,” said Liggett, amused. “He didn’t even turn around to see it.”
When the doctor handed the plants over, they didn’t look like much.
“They were given to us as giant potatoes,” said Liggett, describing how little of the plant’s distinctive exterior had yet to emerge, instead resting dormant under the dirt. “They grew themselves. I just gave them a home.”
Corpse flowers are found in regions of Indonesia where grassy fields meet equatorial forest. Each plant at the zoo is expected to live through about a half-dozen blooming cycles, although some will flower more, Liggett said.
Since their donation in April by Dr. Louis Ricciardiello, an oral surgeon in Laconia, N.H., Liggett has been deluged with questions about their care, which requires extensive accommodation to replicate the environment in which amorphophallus naturally thrives.
A coil of black hose constantly drips water into Morticia’s pot. To prevent insect infestations, the soil must be changed regularly, Liggett said, a chore that takes three people and a front-end loader. Heaters keep the greenhouse at a balmy 82 degrees. Overhead nozzles squirt mist, and a vestibule was built of wood to maintain the humidity at close to 80 percent.
During the past six weeks, Morticia pushed skyward at increasing rates, and in the last four or five days, was measured growing about 5 inches a day. Around Friday the spurt began to slow, Liggett said, a signal that the flower was coming.
The other plants donated are now in their leafing period, when the central stalk regrows into a tougher, shiny, spotted trunk, topped by a tessellated single leaf that to the untrained eye resembles three intricate palm fronds.
As the day progressed and the expectant crowds and temperature swelled inside the greenhouse, Morticia did not.
Despite Morticia’s reluctance to bloom, the scene was enough to give Joan and Bob Brancale a thrill. The Hingham couple were en route to Cape Cod early Sunday, but made a stop after hearing about Morticia’s expected theatrics.
“I came in, and it’s moist and warm, and there is this hushed reverence,” said Joan Brancale, 60, who compared the atmosphere to that of a church’s altar.
“It’s like having a birth.”