Ruth Kassinger's citrus trees are groaning with fruit. The calamondins are brilliant orbs, and the Meyer lemons are perfect yellow spheres on trees adorned with the white blossoms that will spend 2011 swelling into new lemons.

The prize for spookiest citrus goes to the Buddha's Hand, a pendent, handlike fruit with tightly clustered fingers. The award for yummiest goes to the kumquat, a thin-skinned orange relative about the size of kiwi fruit with a sweet rind and tangy flesh. Mind the seeds.

As we munch on the kumquats at Kassinger's sky blue wirework table, I notice the wind outside the conservatory whipping the snow sideways. It's like being in a spaceship and looking out to a cosmic storm, violent but silent.

Kassinger, 56, doesn't see her conservatory as a spaceship so much as a paradise, one full of stimulating paradoxes. In the five years since she added it to the back of her Chevy Chase home, it has become both the sanctuary she envisioned and a link to enchanting tales of tropical gardening in a northern clime.

A science writer and author, she has assembled her conservatory journey into a book, "Paradise Under Glass" (William Morrow, 2010). In it, she recounts her own experiences while peering into the fascinating and sometimes quirky worlds that converge in the artificial jungle. Some of her adventures have been far away, such as the visit to the butterfly farmer in Florida, or just far off in time, to the 19th-century European aristocrats who started the whole conservatory craze with their lavish crystal palaces.

And what is a conservatory, exactly? I think of a greenhouse as a structure where the needs of the plant come first, and a conservatory as one where those of the person prevail. This isn't to say that plants struggle in the conservatory. For all her fretting about insufficient natural light, Kassinger has succeeded in establishing a lush environment and the magical jungle she imagined. The gardener is cocooned in exotic flora: the bright-fruited citrus trees in large pots, a coffee tree beaded with red-brown fruit, banana plants, dracaenas and a beefy schefflera.

There is something deliciously satisfying, regal and slightly decadent in savoring a homegrown kumquat on a winter's day. Now, she thinks nothing of cutting the spiky crown off a store-bought pineapple and growing it in a pot. In time, it sends up a stalk bearing a brand-new pineapple, one ready to be harvested and eaten fresh, not shipped thousands of miles. "Pineapples are so easy," she says.

Tropical swimming hole

If you had told her a few years ago that she would be raising citrus and pineapples in her house, she might have offered a dismissive chuckle. Her husband, Ted, was the gardener, and he focused on the outdoors, the vegetable and ornamental gardens around their 1920s cedar shake house.

Although she wasn't a gardener, she sensed that plants work a magic on the psyche, especially as a jungle of one's own making and particularly in winter. Her epiphany?

A year after she had been diagnosed with breast cancer and her sister Joanie had died of a brain tumor, Kassinger happened to enter the conservatory complex of the U.S. Botanic Garden near the U.S. Capitol. "Vapor languished in the air, and the mugginess after the biting cold outside made me feel almost drugged," she writes in her book. She kept returning, and the end of each visit stirred a recurring sentiment: "It was always hard to leave this place where I felt so thoroughly revived."

The solution seemed obvious. Her own conservatory "would be a perfect antidote to the losses and changes of middle age."

The result was a glazed addition to the house, nestled in the L of its northwest corner. Tall windows define the walls, and the sloping roof is dominated by a dozen skylights. The floor is a light limestone tile, and about a quarter of the space is devoted to a small resistance pool, where the swimmer is kept in place by a strong recirculating current. This might seem a bizarre element of a conservatory, but Kassinger says it indirectly benefits the plants, giving the space the high levels of humidity they need to flourish and ward off the spider mite. The nostrils are spared the chlorine: The pool uses fancy filters and requires minimal chlorine treatments.

The conservatory functions as the family's favorite dining room and a place for Kassinger to work when her attic office seems a bit gloomy. "We eat all our meals here. This is the center of the household now," says Kassinger, now cancer-free.

A budding friendship

One of her worries was that the plants would not get enough light. Through serendipity, Kassinger found Edie April, a plant guru at Johnson's garden center in Northwest Washington who took her under her wing. Kassinger the science writer and April the plantswoman set about choosing plants that inhabit the dark floor of the jungle. In time, Kassinger came to know more plants and their foibles, and learned too that when it came to conservatories, larger is better. Big plants are more in scale and the larger root systems not so prone to drying out.

"When Ruth approached me years ago she didn't know much about plants," says April. "I helped her, but she really took it on herself."

Although the conservatory generated the book, not the other way around, Kassinger's work has helped to form the space.

She discovered that you didn't have to spray against the pests that afflict indoor plants; you can set predatory insects on them. From California, she received 5,000 eggs of the green lacewing. They hatched out into little killing machines in search of mealy bugs, scale and aphids. "I never saw the little larvae, though; they just disappeared into the leaves like invisible guerrilla warriors on a mission."

She came across Patrick Blanc, a French botanist with a global reputation for creating fabulous walls of living plants. After visiting one of his projects in Manhattan, she built her own vertical garden in the conservatory. Following a few missteps, the hydroponically grown mural is now a robust tapestry of leafy plants, among them philodendron, fittonia, pilea and the spiderplant, chlorophytum.

She writes of visiting the butterfly farm in Florida, of seeing the miracle moment when a caterpillar unzips its skin to become a chrysalis, and of raising monarch butterflies in her Chevy Chase jungle.

There is little she would do differently: The limestone stains; a ceramic tile would have been better. And she would have installed larger plants sooner.

The initial idea of conservatory as a retreat alone has changed and grown. It is the sanctuary she sought but not a still one. The citrus go out in the spring, plants are pruned and repotted, pests are tackled anew and the coffee beans are harvested.

As she writes: "A real paradise, it turns out, is not a quiet, immutable refuge, but a place where there is always something new under the sun."

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