Despite heavy foot traffic all year, the trees of Harvard Yard are leafy and shady and the lawn below green and inviting.

Though many people take in the scene without a second thought, a group of 10 students from Norfolk County Agricultural High School wanted to learn about the work behind it. So they listened intently despite Wednesday’s heat as Paul Smith of Harvard’s Landscape Services talked about organic techniques implemented in recent years that are not only more environmentally sustainable but also ensure a healthier Yard.

Smith showed students how Harvard landscapers brew organic “tea” — a mix of compost and other ingredients — in a large water drum near Phillips Brooks House, and talked about soil compaction and root growth and soil microbes. When spread on the Yard’s grassy lawns, the tea promotes a healthier microbial community in the soil.

The students were part of a four-week program — a partnership between their high school and Harvard’s Arnold Arboretum — providing a capstone for their junior year. It blended hands-on work at the arboretum, lectures at a nearby community college, and excursions like Wednesday’s to the Yard and a recent visit to Franklin Park Zoo to see the nearly five-foot-high “corpse flower” in all its stinky glory.

“It’s been a wonderful experience,” said Marc Mertz, an urban forestry instructor at the school and one of the program’s organizers. “The goal is to expose the kids to real-world working conditions and to have an educational component. It makes sense to work with one of the world’s foremost arboretums.”

Kieran Clyne (left) and Paul Smith of Harvard Landscape Services showed the visiting students organic landscaping techniques.

Stephen Schneider, the arboretum’s manager of horticulture and another organizer, said the kids spent most of their time at work in two of the arboretum’s collections. Directed by experienced horticulturalists, the students put in new beds and tended existing beds in the three-acre Leventritt Shrub and Vine Garden and also tended the arboretum’s crabapple collection, in the last year of a major refurbishment.

Schneider was impressed with the students’ enthusiasm and focus during the four weeks.

“I wasn’t this focused as a high school junior. These guys are like lasers,” he said. “This is the prime time to grab their attention — this time of their lives. We know their basic interest is in plants and we want to cultivate that one way or another.”

Though tending the trees and other plants spread across its 265 acres is a major focus, the arboretum also has research and educational goals. Programs such as the one with the Norfolk County Agricultural High School help the arboretum meet the educational portion of its mission, Schneider said.

Sam Sternweiler, a junior who plans to pursue a business degree after high school, said he was interested in landscaping techniques used at the arboretum and in learning more plant identification.

“The arboretum is a world-class place to learn landscape techniques and plant identification,” Sternweiler said. “It was amazing. I wish I didn’t have to leave.”

My microbes