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Tuesday, November 25, 2014         

HAWAII GARDENS


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H-3 construction enabled growth of koa seedlings

By Heidi Bornhorst

POSTED:



Question: There is a koa meadow along the H-3 freeway. It is great to drive above and see the koa growing with other Hawaiian forest plants -- ohia lehua, ieie, uluhe ferns, all so lush and green; it's like driving through a rain forest. The meadow created by construction had lots of sprouting koa seedlings, but they were soon overtopped by weeds growing rapidly and smothering them. Our ohana drove over during the big rains and saw that the koa was all cleared -- there were no weeds. Who is doing this? I want to salute them. -- Bobby Obata

Answer: Chris Dacus of state Department of Transportation is an advocate for native plants and commonsense highway plant maintenance. Hawaii plant and land restoration experts Matt Schirman and Rick Barboza of Hui Ku Maoli Ola were subcontracted for the job. It is not easy work.

"Halawa is a special place. DOT is trying to be a good steward of the aina.

It's always best to deal with weeds before they go to seed or, in the case of weedy vines, before they get 90 feet up into the trees. And as any home gardener or maintenance professional will tell you, it always takes longer than you think. In a blink the weeds are back again, more vigorous than ever, if you don't get them out by the roots or if you let the seeds fly around.

One of the major pests in the koa meadow is that horrible weed vine that we call maile pilau. It looks something like maile but the smell is horrid. It has pretty, small flowers that are followed by fruit with numerous seeds. The fruit are orange, and that is a color that birds see and like to eat, spreading the weed seeds with their kukae (excrement).

Maile pilau also has thick, spreading storage roots. You cut the top and pull some, but if you leave even a bit, the vines will soon be back.

The weed control and planting project started in February. "In parts of the H-3 the entire understory is maile pilau," Rick said. "Forest floor and tree canopy are linked together with pilau vines. It's terrible. ... You risk breaking a koa branch trying to get rid of the weed. You have to be very gentle when cutting down weed trees tangled with weed vines.

"One better method we found is to cut the vine runners off around the koa trees first."

The crew also cut down more than 3,000 guava bushes while planting 1,300 koa and 250 native white hibiscus.

The 4-acre koa meadow was a staging and stockpile area and parking lot during freeway construction. Koa seeds blew in from adjacent good forest and popped up after the parking area was removed.

"Then the guava trees ate up the whole area," Rick said.

Dacus also thanked forester and koa advocate Nick Dudley, a researcher for Hawaii Agriculture Research Center. Dudley thinks this is one of the best koa forests on Oahu. It is resistant to koa wilt disease. "Isn't it amazing that one of the best koa forests on Oahu is a result of a highway project?" mused Dacus. "This is a great opportunity for perpetuating a diverse native forest. There is also a plan to plant loulu palms."

Heidi Leianuenue Bornhorst is a Hawaiian horticulturist, arborist, food gardener and sustainable landscape designer. Email her at heidib@hawaii.rr.com.






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