On a recent Sunday afternoon, Kevin Zhang painstakingly removes an $80 pitcher plant from his plant fridge, gently untangling its bulbous pitchers so as to not rip them. He keeps the plant inside the refrigerator because, come nighttime, it needs a steep drop in temperature.

“Careful,” Sarah Santucci, Zhang’s partner, calls from across the room. “It’s caught in the wires. Do you need help?”

The couple, both 24-year-old medical students at the University of Pennsylvania, are in Zhang’s small Graduate Hospital apartment, which brims with thousands of plants. Most of them are carnivorous, requiring particular habitats, watering, and feeding schedules. There are clusters of pitcher plants of all sizes and colors, butterworts with sticky leaves that ensnare unlucky bugs, and bladderworts, which grow in water and catch mosquito larvae and water fleas with tiny traps on their roots. They feast on fruit flies from Zhang’s compost bin (and occasionally fertilizer pills).

These two plant lovers are doing their best to keep their most impressive specimens in flawless shape, in preparation for the Philadelphia Flower Show’s annual plant contests. It’s a yearly tradition for the young couple. When March arrives, they carefully prune their flora, load them into a car, and deliver them to the Convention Center.

Each year, the Flower Show holds hundreds of contests for gardeners and growers who compete for ribbons from the Pennsylvania Horticultural Society. The categories are divided by plant species and skill level, and they draw throngs of entrants and onlookers to the Hamilton Horticourt, where judges evaluate plants on their health, distinctiveness, quality, rarity, and difficulty to grow. Participation guarantees you a free ticket to the show, and if your plant wins, you’re rewarded with a ribbon as well as points.

“The first year I did it, I thought, ‘Well, I might as well try it,’ ” Zhang says. He has accrued dozens of ribbons since his first year of competition in 2017, when he befriended Stephen Maciejewski, president of the Liberty Bell Gesneriad Society. (Gesneriads are a family of flowering plants, the best-known of which is the African violet.)

“He was entering some carnivorous plants, especially a very beautiful Nepenthes “lady luck” that caught my eye,” Maciejewski says. “Last year, he entered Cephalotus follicularis — a small, strange-looking, maroon-colored plant like something out of Little Shop of Horrors — that everyone wanted.” The plant won a blue ribbon.

Kevin Zhang keeps his plants all over his Graduate Hospital-area apartment.
Kristen Balderas
Kevin Zhang keeps his plants all over his Graduate Hospital-area apartment.

“I was really surprised with the results,” Zhang says. “It felt very validating to have plants out there that people think are really cool.”

Millennials’ love for houseplants has been well-documented in recent years, but Zhang’s passion bloomed well before his teenage years. He has been growing plants since the first grade.

Zhang became interested in them after watching his grandmother pick worms off tomato plants in her garden. Growing up in Chicago, he passed on the chapter books his classmates read during their after-school program — poring over a plant textbook instead, meticulously highlighting as he went along.

By third grade, Zhang’s interest in plants had become so serious that his dad took him to a cacti nursery in Illinois, where he encountered carnivorous plants like Venus flytraps and sundews for the first time. It was at the nursery that Zhang persuaded his father to buy him a few flytraps, marking the beginnings of his carnivorous plant collection.

“I was instantly hooked,” says Zhang, who has lived in Philadelphia since 2005. “I just thought they were really nice to look at. I think they’re beautiful.”

At home, Zhang embarked on a years-long quest to grow a giant pumpkin in his backyard. (He managed to grow a 20-pounder in high school; his parents promptly chopped it up for homemade dumplings.) His plant collection followed him to a dorm-room aquarium at Princeton University, and then to Philly for medical school.

Kevin Zhang pulls a pitcher plant out of his aquarium, which provides the high humidity the plants need to survive.
Kristen Balderas
Kevin Zhang pulls a pitcher plant out of his aquarium, which provides the high humidity the plants need to survive.

He picked this top-floor apartment for its roof access. There’s a small greenhouse there for plants that are currently dormant, along with pumpkins and summer vegetables. Zhang said moving the trays of plants was tricky because you can’t stack them.

“My dad and I made countless trips up and down the stairs,” he says with a sheepish smile.

Santucci is well-equipped to embrace Zhang’s plant obsession. The Mississippi Delta native began growing orchids after a visit to the Philadelphia Flower Show when she was in the seventh grade.

Unsurprisingly, plants played a role in how the pair met: They struck up a conversation at an activities fair at Princeton when he was a sophomore and she a freshman.

“I was running the table for the botany club and had a few pitcher plants in an aquarium,” Zhang says. “And Sarah came by and was like: ‘Oh my gosh! Is that a Nepenthes?’ and I was like, ‘Oh my gosh! You are literally the only person who knows what that is!’ ”

Zhang has a second refrigerator to store plants that need to be kept at a low temperature.
Kristen Balderas
Zhang has a second refrigerator to store plants that need to be kept at a low temperature.

The couple would hand out home-grown herbs and mistletoe to their classmates during their time as members of the botany club.

Today, Zhang keeps most of his plants under grow lights in trays filled with distilled water, which flows from a reverse-osmosis system he installed on his kitchen faucet. Sick plants are kept on an isolated shelf for special monitoring. Zhang has devised ways to care for the more finicky species, using an aquarium to provide 100 percent humidity for tropical plants. Temperatures are tracked by probes. The one-bedroom apartment has a lab-like atmosphere.

“I just have a personality that’s interested in research,” Zhang says. “With plants, I couldn’t just give up when I failed. I think that’s what drew me to this.”