Roofing material doesn't usually attract much attention, but there's something special about the one planned for the new Fallbrook Library.

"We've had people calling from all over about this," said Jerri Patchett, chairwoman of the Friends of the Fallbrook Library building task force. "They want to know about the art and the green roof."

"Green" usually means a building is environmentally sensitive, but it has a more literal meaning with the library's roof, which will be covered with 3,300 square feet of living succulents.

Most of the succulents were planted last week in 4-by-2-foot trays at Altman Plants in Escondido, and on Monday an open house was held just for the curious to take a look at the innovative design.

Few people had arrived by early afternoon, possibly because organizers had little chance to get the word out about the quickly arranged event, Patchett said.

Builders broke ground on the 20,000-square-foot library on Main Avenue in September, and the $11 million building is expected to open early next year. Friends of the Library have contributed about $2.3 million to the project.

Dave Batey, vice president of client relations for Fallbrook-based Executive Landscape Inc., said his company will haul and install the 504 trays sometime in October. Each tray is eight square feet and can weigh up to 25 pounds a square foot when wet, he said.

The roof will be made of concrete and metal to withstand the weight, and water will drain from holes in the sides of the trays.

This will be the second live-plant roof in the county installed by Executive Landscape, Batey said. The first was the multilevel Strata apartment building at 10th Avenue and Market Street in downtown San Diego, where Batey helped install 7,000 square feet of plants on the roofs of the fifth and 24th floors.

Only residents living above the fifth floor can see some of the plants, while only people in airplanes can see the ones on the top. But while largely unnoticed, the plants do go toward points in the Leadership in Energy & Environmental Design program, an industry certification system that recognizes energy savings, water efficiency, CO2 emissions reduction and improved indoor environmental quality.

Unlike the Strata building, the roof of the Fallbrook Library will be at an angle and will be visible. Patchett said she expects it to turn some heads when motorists see it.

"People will turn the corner and want to see just what is this building."

Patchett said the trays will be arranged to form a colorful abstract pattern once the plants are in place.

John Bagnasco, marketing director of Altman Plants, which he described as the world's largest grower of succulents, said the concept of using living plants on roofs is new and hasn't worked in every climate. In San Diego, where not every plant would work well on a rooftop because of low rainfall, Bagnasco said Altman is confident these succulents, called sedums, will thrive.

Batey said the roof will be watered with a low-volume spray system. While he doesn't yet know how much water the plants will take, he expects them to be watered every few days in the summer and not at all in winter.

Call staff writer Gary Warth at 760-740-5410.