Native plants prove costly, difficult for highway landscape

seeds and nursery equipment Using native grasses and other indigenous plants to landscape the median and shoulders of Mokulele Highway made sense, especially when advocates said the greenery would need less water and a minimal amount of maintenance.But establishing the native species is proving costly and challenging. State officials estimate it could cost nearly $1 million a year to maintain the native plant landscaping along the newly widened Mokulele Highway. Using traditional Bermuda grass could have cost half as much. The state’s estimate for the maintenance of the native plants “is based on our observations of the amount of manpower needed to keep it in an optimum-looking condition,” said Charlene Shibuya, a Maui engineer with the Highways Division of the state Department of Transportation. Shibuya estimated costs could be around $936,000 a year to maintain the 6.5 miles of native grasses, shrubs and trees. Estimates do not include equipment, fuel and chemicals. Work involved would include weeding, fertilizing and using herbicides to keep the plants healthy and maintained, she said. Last week, Shibuya along with other state officials and residents celebrated the completion of the $87 million Mokulele Highway widening project from Puunene Avenue to Piilani Highway. With it, the state unveiled a separate bike path and its first highway on Maui landscaped with native plants.The native plants cost $8.1 million, which includes a three-year maintenance period, Shibuya said.State and federal highway funds paid for the widening project. The funds are supplemented by taxes on fuel and vehicles. Once the native grasses and plants are established and the state’s contracted maintenance period ends, the temporary sprinkler systems will be removed, Shibuya said. Bermuda grass, the common grass used along most state highways, is a perennial grass that can be grown by seed and also is commonly used on playing fields. The akiaki grass, or Sporobolus virginicus, is a native perennial grass. As a cost comparison, Shibuya said the akiaki grass along Mokulele costs about $57,700 per acre, while the traditional Bermuda grass costs could range from $21,900 to $35,500 an acre. She based her estimate on the state’s use of Bermuda grass for the Haleakala Highway widening project.