Another invasive weed — glycine — is spreading widely across isle
Highway workers hired to cut back vine that covers guardrails, signs
Maui’s state Highways Division is looking to add at least 10 workers to help clear out thick cane grass along the road and glycine — an increasingly pervasive vine that blankets guardrails, road shoulders and road signs, state Department of Transportation officials said.
“That vine has definitely spread all over the place,” District Engineer Robin Shishido said Wednesday. “I live in Waikapu, and it’s in my backyard. You see it all over the place. It’s amazing how it can grow through the signposts.”
Related to the common soybean, glycine was introduced to Hawaii after a massive kikuyu grass dieback in the 1970s, according to the Maui Invasive Species Committee. The Soil Conservation Service, now known as the Natural Resources Conservation Service, recommended the tropical vine for pasture improvement and forage for ranches.
Ulupalakua Ranch was believed to be the first ranch to experiment with the vine. While grazing animals loved it, the vine quickly spread throughout Upcountry and East Maui — most likely on the feet of hoofed animals.
“It’s pretty widespread and unfortunately not something MISC can control,” Manager Adam Radford said Wednesday. “I would say glycine has yet to fully occupy the island. It could occupy most dry to wet forests below 4,000-feet elevation. It’s a good example of a classic invasion curve — when a new thing shows up and really takes off, it suddenly becomes apparent to the community and raises alarm bells.”
Upcountry residents have asked the county and state to clear the invasive vine due to road safety concerns and the destruction of the area’s iconic jacaranda trees. About a hundred people gathered for an update late last month at the Kula Community Center.
“I told them, ‘You folks have to keep on top of it because most of us up here are old already and can’t be going and trying to keep control of it,’ “ said Barbara Fernandez from the environmental nonprofit Maui Green & Beautiful.
Fernandez urged residents and the community to help remove the plant manually by cutting it and then pulling the roots a few weeks later. She said she hopes the community clears enough to see the jacarandas bloom.
“Those of us who live Upcountry, we love it,” she said of the purple-flowered trees. “It makes us feel good when the jacaranda trees come and bloom. The tourists come up, so economically it has an impact. They go to the restaurants just to look at it.”
Radford said it is unknown what the “true impacts” of the plant are for the island, but it does pose some potential environmental threats. So far, though, “it doesn’t come close” to other invasive species on the island such as the axis deer and little fire ants.
“There’s really no comparison,” he said. “It’s beyond the scope and scale that our resources allow. We also don’t know or believe it will have the environmental impact that something like little fire ants have.”
The vines still present an issue for motorists when they completely cover guardrails or signs, as well as wrap around telephone poles and electric lines.
“If you go up Pukalani through old Haleakala Highway, it’s wrapped around like crazy over there,” Shishido said. “Once that thing gets in somewhere, it’s pretty invasive.”
Highway maintenance crews have been undermanned for some time, and coupled with recent rainy weather the vines have taken a foothold alongside tall cane grass, Shishido said. Guardrails covered by glycine are more prone to rust and give motorists the illusion of a bush, while tall cane grass can block sightlines.
“Cane grass grows fast and tall. If you don’t cut it, it’ll grow 6 to 8 feet tall and then it leans out over the road,” he said. “It’s a really hardy weed. If you keep cutting it, it keeps getting thicker and thicker.”
Progress also slowed after crews stopped using herbicides such as Roundup due to community concerns, Shishido said. Organic alternatives and regular trimming struggle to keep pace.
Crews have recently restarted using the weed killer in small doses, but remain sensitive to residents’ concerns, Shishido said.
“We’re not wholesale spraying with a large tractor,” he said. “We’re keeping away from water areas and sidewalks, and only using it in priority areas.”
* Chris Sugidono can be reached at firstname.lastname@example.org.