In 1899, amateur botanist John Morris and his sister Lydia built a “jewel” on the property of their summer estate, Compton.

This fernery, a glassed home for ferns, rimmed by a foundation of stone, perfectly tapped into the Victorian era fascination with the plants. Fascination, however, may be an understatement.Some say the Victorians were downright obsessed. The term pteridomania describes this fixation on ferns: Forms of the plant appeared on textiles, pottery, furniture, and even gravestones.

But the Morris siblings were not just dabbling in the trends of the day; both John and Lydia were serious about their hobby.

They hired the architectural firm of Hitchings & Co. to draw up blueprints for the fernery. A Japanese gardener and craftsmen designed and set the rocks in the interior of the structure. One thousand ferns were ordered from Birkenhead Nursery to populate the structure.

Today, this throwback to the Victorian era still stands on the Morris’ old property, which is the present-day site of the Morris Arboretum.

While the fernery slowly fell into disrepair in the century after its initial construction, it was fully restored and reopened to the public in 1994 as the Dorrance H. Hamilton Fernery. It is the only remaining freestanding Victorian fernery in North America.

The fernery is a uniquely warm respite during the cold months, as it is heated to 63 degrees—though it does get warmer inside the glass walls during the middle of the day. Most of the fernery’s collection was put in place at the time of the massive renovation in 1994, and includes temperate plants that can be grown in climates like San Francisco, the Pacific Northwest, or England, says Shelley Dillard, propagator at the Arboretum.

Unlike other spaces at the Arboretum, the fernery is not curated, which means Dillard and her team of nine volunteers can remove ferns when they grow too wild, and add new ferns to the mix. It’s a delicate balance, she says, of grooming and letting the plants naturally populate areas inside the fernery.

“We let them grow how they’re going to grow,” Dillard says.

There are, however, a few rules to the fernery—the only plants inside are those that reproduce by spores (so no flowering plants such as begonias or orchids). And like the few other remaining fernerys in Scotland and England, visitors step down into the Arboretum’s space; the fernery also has an overlook, a tunnel, a water feature, and a bridge. Fernerys are usually made out of the local stone, which, in this case, is Wissahickon schist.

“It’s the gem of the Arboretum,” says Dillard. “I love working in here. It’s just wonderful.”