LAKE CITY — It may be South Carolina’s most beautiful roof that very few ever see.

But the experimental green roof here at the Moore Botanical Garden is designed not just to delight visitors who climb up the circular metal stairs.

It’s designed to help architects, property owners and others get a better understanding of what kind of plants will survive, even thrive, on a roof in a hot and humid southern climate.

Matt Lobdell, a research assistant with Moore Farms, spends part of his week surveying and tending the approximately 130 plant varieties on the roof. He noted most green roof research has been done in Europe and northern America — different climates from South Carolina’s.

“What we’re really trying to do is try some new plants on green roofs that haven’t been done in the Southeast before,” Lobdell said.

The idea of creating a “green” roof — one covered with soil and plants — actually originated in Scandinavia, said Joe Rogers, the architect who designed the building and its roof.

“They would build a wooden structure and put sod on top of it as a roof material,” he said. “The plant material absorbs a lot of energy from the sun. You don’t get a lot of temperature extremes on the roof membrane.”

Rogers said the multipurpose farm building houses vehicles, a woodworking shop, a paint shop and offices, so it was going to be built durably — strong enough to house a green roof and the 60 pounds per square foot of pressure it adds.

Ultimately, the sloped roof was covered with a series of membranes and six inches of soil, and zoned into several grids, each with a different set of plants. The rainwater that manages to trickle through the plants and soil is caught and directed into a cistern, which is used to irrigate the roof during dry spells. A series of sensors keeps track of the conditions.

Garden director Ethan Kaufmann said the plant varieties on the roof are extremely diverse, “or everything but the kitchen sink.” It includes natives, exotics, bulbs, annuals, vegetables, shrubs, vines, and perennials.

The garden’s goal is to study which plants do well on a roof as well as to create something of beauty.

“When we take visitors on the roof and see their reactions, it’s not only rewarding, but also lets us know we’ve been successful in our goal,” he said. “Believe it or not, nearly everything has performed better than we thought it would. This has actually led to us having to thin some of the plants.”

The green roof proved so popular that Moore later designed a catwalk —a flat section covered in turf — that lets visitors and horticulturists easily walk along the roof. At each end of the catwalk is a spiral staircase that makes access easy.

“They were spending a lot of time going up there recording the data and how the plants were performing,” Rogers said. “It got to be a safety concern.”

Kaufmann said Moore Farms plans to post all results on the website later next year, after it has at least three years of data. Lobdell also will discuss the findings at conferences, such as the national green roof conference. And Kaufmann said some seeds from strong performing roof plants already have been sent to an Atlanta nursery.

“It’s probably most important to involve the nurseries,” he added. “They are the ones who will ultimately provide designers with the material they need.”

Reach Robert Behre at 937-5771.