If a golf course can have a New Year’s resolution, Ko’olau Golf Club’s would be to see the light in 2017.

Since it opened 25 years ago, Ko’olau has been known for its drastic difficulty as much as its astonishing beauty. Its views are to die for. So is its propensity for eating golf balls and making mud.

It is cut into 242 acres of tropical rain forest that is designated a nature conservancy, home to three climate zones next to the Ko’olau Mountains. There are steep elevation changes, six massive ravines, huge bunkers and lush growth that has overwhelmed the course in recent years.

It was a jungle out there.

Early on, it was marketed as the toughest course in the country. Its first course rating was 162 — so high the USGA rejected it. It sent its own team out to rate it again, and it came back with a 172 degree of difficulty.

Today, that rating is 153 from the black (back) tees and, ideally, plummeting.

A month ago, South Korea’s YHB Hospitality Group took over the lease. It also has the lease on Royal Hawaiian and now owns Mililani, Hawaii Kai and Ewa Beach, along with hotels and golf courses in California, South Korea and Japan.

For the last three weeks, “a jungle’s worth” of trees have been taken out, in an attempt to let the course see the light, according to general manager Ken Terao. He said some areas — the 15th green a prime example — were so overgrown you never saw the sun.

“The greens were dying,” he says. “Our biggest complaint was always mud, mush, muck. Every time it rains it takes weeks to dry up. There was absolutely no air flow, no sunlight on the fairways and greens. People said the course felt claustrophobic because trees were growing over both sides.

“The key reason why we started with the trees was first, to improve air flow and allow us to recover greens and so the fairways will be dryer. Plus, now you can see the course and that is just amazing.”

In three six-day work weeks, the back nine has been transformed. The sun is visible again, along with fairways, greens and only-in-Kaneohe views.

The 11th green is coming back and its fairway opening is now wider than 20 feet. You can see the Pacific Ocean again from the 12th tee, and almost the entire back nine. The course’s one lake, along the 16th green, is now visible from the fairway. Rock walls and bridges, which had disappeared over the years, have re-appeared.

The front nine is next. Then there are plans to improve drainage, replace the fairway grass and lots more, to bring Ko`olau back to the prominence it once held. Golf Digest ranked it among its top new, toughest and public courses.

“It’s at least 100 percent better already,” Terao claims. “The greens will take a couple months. They’ll be fixed by the time we aerate in April. Already they are getting sunlight. All the algae and fungus are dying because we’re getting sun and air now.”

The goal is to return to what the course looked like when it opened — after an $82 million investment — in 1992.

“They had everything down to shrub level then,” Terao said. “Course conditions now have a really good chance of improving. The playability will be better, the greens quality better, everything will be better.”

And all those golf balls that have been uncovered the past three weeks —one slope was practically white — will be pretty much gone.

The unwritten rule at Ko’olau over the years was to bring at least as many golf balls as your handicap. Often, it wasn’t enough and employees had to keep an eye on range balls, which had a habit of disappearing into golf bags.

It is probably still the toughest course in Hawaii, but no longer the nation. Terao put in “hybrid” tees two years ago and moved tees that required 200-yard carries on six holes across ravines.

He hopes the last three years of 100-plus inches of rain are over, but even if it isn’t he has hope. The course took on three inches of rain during Saturday’s storm, but by Tuesday the newly opened fairways were dry. And he doesn’t believe it will take long recently cleared areas to green again.

It is a rain forest and, even at its toughest, Ko’olau has always been serene and spectacular.

“It is challenging, but we have tees to make it more friendly if you want to have a better time,” Terao says. “It’s just the ambience, the sheer beauty. There’s no course that can match it.”