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plants in planter bed filled with mulch
Plants maintained with mulch in the Hawaiʻi Institute of Geophysics courtyard

The lush plants and trees of the University of Hawaiʻi at Mānoa Campus Arboretum provide a vibrant environment for research and recreation, making it one of the most beautiful campuses in the world. The health of those flora are in part due to an initiative to manage green debris on campus and make mulch (material spread around or over a plant to enrich or insulate) 100% from campus resources.

Green debris from UH Mānoa facilities are processed in an on-campus machine called a forestry tub grinder, creating organic mulch that helps regulate soil temperature; retains water and reduces water usage; adds micronutrients to flora as it decomposes; helps suppress grass or weeds competing for water and nutrients; and adds to the beautification of the campus.

Green debris grinding saves the green

Previously, the landscaping department utilized a chipper to help break down green debris, and large green debris that could not fit in the chipper was transported to Hawaiian Earth Products in Wahiawa—two to three truckloads were transported per week. Moreover, landscaping had to purchase mulch when the in-house supply fell short.

Once the tub grinder was introduced to the campus in 2010, landscaping was able to more effectively grind the campus’ green debris down to organic mulch. With the expertise of Siausage “Sonny” Ugaitafa, one of the equipment operators who processes the green debris, the campus was able to go from turning 30% of green debris to mulch in 2010, to 70% in 2017, and now 100% reusable mulch.

plants with mulch

“Our mulch initiative has developed significantly over the past decade,” said UH Mānoa Landscape Manager Yosuke Jo. “Since we are able to produce 100% sustainable mulch on-campus, we save nearly $500,000 a year in transportation and mulch purchase costs. We hope to continue our mulch initiative with improved technology.”

Ugaitafa received a Presidential Award for Outstanding Service for his work in the mulch initiative. He helped identify designated areas for green debris pick up and removal while ensuring the campus remains safe and upkeeps aesthetic standards.

“The process to create 100% sustainable mulch has been very efficient,” said Ugaitafa. “I’m proud to play a major role in the campus’ mulch initiative, and the health and beauty in our campus plants and trees is a testament to the landscaping department’s hard work and dedication to the initiative.”

The landscaping department also distributed mulch to Kapiʻolani Community College, UH West Oʻahu, the Hawaiʻi Department of Land and Natural Resources, the reforestation project Kūkaniloko and others.

Battle against beetles

Mulch is a common breeding ground for the coconut rhinoceros beetle (CRB), a pest known to kill and damage the native endemic Hawaiian loulu, a palm tree with fanned fronds, which grows in protected populations due to their threatened and endangered status.

The landscaping department remains diligent in the battle against CRB in their mulch initiative by carefully monitoring the green debris that is processed; maintaining CRB compliance with the Hawaiʻi Department of Agriculture interim rule 22-1; and, since October 2022, only exchanging with entities that are also CRB compliant.

Furthermore, the landscaping department participates in training sessions to remain up-to-date and educated on CRB. Led by Michael Melzer, an associate researcher in the College of Tropical Agriculture and Human ResourcesDepartment of Plant and Environmental Protection Sciences, landscaping staff attend an in-person classroom lecture that discusses the history, biology, symptoms and control methods available for CRB, followed by a visit to the containment lab to see CRB larvae and adults. Landscaping leadership also receive CRB compliance agreement training.

“[The landscaping department has] been very engaging and keen to keep the beetle off campus,” said Melzer. “I am impressed by their genuine concern for how the campus looks, and am thrilled every time I get a question as to whether they are seeing CRB damage.”

plants in mulch

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