Reaching from a stepstool to retrieve a bromeliad from the top shelf, Cathy Umphrey is bathed in light. The edge of her long brown ponytail turns amber as sun splashes through glass. She sets the clay pot on a waist-high table, pushes up the sleeves of her blue cotton sweater, and bends to inspect the leaves. Outside is the steely cold of winter, but inside her greenhouse, Umphrey has a nine-by-seventeen-foot patch of summer. “Having worked in nurseries for ten years, I realized how heavenly it would be to have a greenhouse space in the wintertime,” says Umphrey, director of horticulture at Historic London Town House and Gardens, a twenty-three-acre park in Edgewater that was a colonial tobacco port.

So when the roof of the stand-alone garage behind her 1930s Annapolis bungalow was about to give out, Umphrey decided to splurge. She called Doug Sanner, a general contractor who’d built greenhouses on properties where she’d worked. He’d never done a greenhouse retrofit but deemed the site worthy of a try. Together they planned a design, procured permits, and searched for the right materials—not easy given that most greenhouses come as complete kits to be built from the ground up.

She knew she wanted knee walls—short walls that support windows, like in sunrooms—along which she could build storage space. “I didn’t want the entire wall transparent. Greenhouses are messy, and everything in plain sight would ruin the tranquility of my garden.” She also wanted glass for the glazing, “but it’s expensive and it breaks—not a good thing when limbs fall from our neighbor’s tall locust tree.” Instead she chose triple-walled polycarbonate, a clear plastic with air spaces to hold heat. “It’s accident-safe, weather-resistant, and easy to replace if a panel is damaged,” Umphrey explains.

Umphrey traces her passion for gardening to the days when she and her husband, Stewart, a philosophy professor, lived in a third-story Greenwich Village apartment. “Until then, I had taken for granted my appreciation of the natural world,” she says. Stewart built her a three-foot-long window box.

After the couple moved to Oklahoma, Umphrey completed a master gardening course “just for fun.”

In 1984, they headed east (her husband joined the faculty at St. John’s College in Annapolis), and she expanded her horticulture knowledge while working at a series of nurseries. Later she launched an independent garden design service, helping people install landscaping and flowerbeds.

“I love putting plants together in a way that is greater than the sum of their parts,” Umphrey says, a knack evident in her own compact backyard, which during the growing season spills over with coleus, amaranth, herbs, and blossoms.

She was nervous during the greenhouse’s three-month transformation, completed in January 2003. “I was afraid the entire structure would be hideous. What if I wouldn’t want to go in the backyard again?” But the result has the lure of a child’s old-fashioned playhouse and the functionality of a greenhouse and storage shed combined. Most of the south wall is transparent to take advantage of the sun, while the north wall is solid for hanging shears and rakes and stacking clay pots. The original redwood exterior is painted a soothing blue gray. For an extra touch of charm, Umphrey selected a white Dutch door for the entrance—a style once used in farmhouses to keep animals from wandering in—with a windowed top that opens separately from the bottom. “I’ve gotten ribbed about the wooden door, because it expands and contracts from humidity. Fiberglass would have made more sense, but I prefer natural materials.”

Creating an affordable interior to suit her needs required a good dose of imagination. Pots sit on chicken-hatching shelves salvaged from an incubator. A worktable on coasters, where she examines plants for bugs and diseases, is topped with a sturdy slab of limestone donated by a neighbor. Old tin oilcans with spouts serve as watering cans. To squeeze in a potting area, Umphrey devised a ledge on hinges she can close when she doesn’t need it. A refrigerator for storing seeds sits under a growing table the length of one wall, which has a sink at one end and a heat mat across the top, set at 70 degrees to keep seedlings warm. The floor is built of red pavers, easily hosed down when mud is tracked in.

When you look around her greenhouse, it’s clear that Umphrey is drawn to succulents—cacti, aloe, and other plants that store water in their tissues. “I love their form; it reminds you that there are many different ways for plants to grow that are unconventional and don’t fit the mold.”

She also loves bromeliads, a family whose most famous member is the pineapple. Umphrey’s favorite is the earth star bromeliad, with banded red leaves radiating from a central point. “I enjoy orchids and amaryllis, too, and weird vegetables.”

She collects seeds from plants no longer widely cultivated, such as orach, a purple-green spinach-like vegetable eaten regularly in colonial times. Her first project after completing the greenhouse was to start seedlings for the Anne Arundel County Farmers’ Market, where she sold a “weird vegetable of the week,” such as purple Brussels sprouts. Although it was more for fun than a money-making venture, Umphrey likes knowing that her greenhouse could be used for profit if necessary.

She spends at least a full day a week in the greenhouse, sometimes more, watering, fertilizing, cleaning, and checking each plant. Evidence of her success is in the leaves, blossoms, spikes, and spirals that surround her. “The biggest challenge is that you’re in complete control. When you garden outside, you don’t realize the extent to which you rely on the benefits of Mother Nature. In the greenhouse, you are the sole provider of water and nutrients; you have to make sure you have bugs under control, keep the temperature right—it’s easy to lose balance,” she says. “This is my place to be quiet and contemplative—my own private getaway. When the humidity is just right inside, it’s like stepping into a spring day.”

Vicki Meade is a freelance writer living in Annapolis.