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Day by day, twig by twig, National Bonsai and Penjing Museum curator Warren Hill trains a remarkable collection of tiny timber.

Young Choe kneels in a back room of the U.S. National Arboretum’s National Bonsai and Penjing Museum off New York Avenue NE, staring at a forest of miniature olive trees. She takes a toothbrush and scrubs at the outcrop of rock that supports the grove of bonsai. She then picks up a patch of moss sitting in a nearby dustpan. The moss is from another bonsai that had too much; the scene in front of Choe has too little. She breaks off pieces of moss and presses them here and there against the naked rock. Stepping back, she picks up a spray bottle and pulls the trigger. Gusts of mist roll across the landscape.

Warren Hill, the museum’s sole curator, walks by and pauses to inspect Choe’s work. As soon as Hill is satisfied, the bonsai landscape will be put back on display.

For now, Hill and Choe, a graduate student in horticulture at the University of Maryland and a volunteer at the museum, fuss with the trees, picking at the canopy and poking at an exposed root. Hill aims his finger at a point of particular interest: “Eventually,” he says, “this tree will split these rocks.”

“Then what do we do?” Choe asks.

“We let nature take its path. It’s what would happen on a mountain.”

Despite his advice on this occasion, Hill is not what you would expect from a bonsai master who has lorded over our nation’s premier collection of miniature trees for the past five years. For one thing, he’s not even Japanese-American.

Hill, the son of American parents of Scandinavian descent, was born in Minnesota in 1938. He grew up in Northern California and spent the majority of his life working as an engineer in the electronics industry. He stumbled on the ancient art of growing Lilliputian trees in 1960, when interest in bonsai was exploding in North America. He “got into bonsai by accident,” he says, when he walked into an exhibition called “What Is Bonsai?” at the California Museum of Science and Industry in Los Angeles. “I didn’t know what I was looking at,” says Hill, “but I knew I had to learn more about those little trees.”

Inspired, Hill bought some books and began teaching himself bonsai. But after five years of mediocre results, he knew he needed help. “It’s an awfully tough art form to learn from a book,” he says. So he joined one of Southern California’s many bonsai clubs to learn from other local enthusiasts. “I realized that it’s a lifetime learning process,” says Hill. “You ascend from level to level—if you push yourself.”

Hill kept pushing himself to improve, and after 10 years of refining his skills, he received an invitation to join the California Bonsai Society, the most prestigious bonsai club in North America, which was established in 1950. Under the tutelage of John Naka, the Michael Jordan of North American bonsai, who still lives and teaches in Southern California, Hill continued to hone his craftsmanship. Over the next two-and-a-half decades, Hill’s love of bonsai took him to Taiwan, Japan, England, and Colombia—and ultimately landed him in D.C.

“I was semiretired when this position came up,” he says. “I was going to sit on my front porch in Tennessee, sip on mash, watch the sun go down, and play with my little trees.” But in 1996, the National Bonsai and Penjing Museum needed a new curator. Despite having to postpone his retirement, Hill took the job, which he saw as an opportunity to give something back to the art form that had given him so much satisfaction.

There’s a bonsai proverb that states, “You not only work on the tree; the tree works on you.” Hill, like many bonsai enthusiasts, believes that working on bonsai keeps you young. “There’s so much anticipation. You may be looking five years down the road and getting excited about it. You think to yourself, Wow, in five years, this little branch will be twice as long. It gives you a reason to live.”

Although Hill might be able to cultivate youthfulness through his job, others in the same position might wither from the pressure. As any bonsai rookie will tell you, bonsai grow slow, but they die fast. Hill laughs off the suggestion that he has found the one high-stress job in the whole bonsai world.

Each day, Hill plays chaperone to an illustrious group of thoroughbred bonsai. The oldest tree under his supervision is 375 years old. For more than 130,000 straight days, this Japanese white pine has been dutifully tended to by six generations of bonsai masters. But in just 48 hours of neglect, the tree, worth hundreds of thousand of dollars, could die.

With a full-time staff of just four, Hill doesn’t have time to personally pamper one bonsai more than any other. “Without the help of the volunteers, it would be impossible,” says Hill, referring to the 25 or so individuals who come to the museum once a week to help out.

When he’s not caring for the collection, Hill’s designing seasonal exhibits, planning for scholarly symposiums, and working to educate the public. Question No. 1: What does penjing mean? Hill answers this one all the time. The art of growing miniature trees, he says, originated around 5000 B.C.E. in China, not Japan. The Chinese term for the art form is penjing.

You can make a bonsai or penjing out of just about any kind of tree. When a bonsai-obsessed person like Hill goes for a walk in the woods, he or she usually comes back with seedlings. “I get my inspiration from nature,” Hill says. “A teacher of mine once said that one trip to nature is worth 10 workshops.”

Many of the museum’s bonsai came from overseas. But when it comes to importing bonsai, government regulations are often trickier to negotiate than the finicky plants’ biological jet lag. It’s a lesson former President Richard Nixon learned the hard way.

In 1976, employees of the U.S. Department of Agriculture boarded Nixon’s personal jet at Los Angeles International Airport and confiscated an illegal penjing. Nixon was bringing the tree, which was a gift from Mao Tse-tung, back from a trip to China.

Back in 1972, Mao had given Nixon eight other penjing, which, until Nixon’s resignation, stayed with the president at the White House. Despite their great value, Nixon never registered the trees with the White House Gifts Unit, as required by the Foreign Gifts and Decorations Act of 1966. But before Nixon could leave office with the trees, Philip Buchen, legal counsel to President Gerald Ford, interceded and persuaded Nixon to leave the trees behind. The estranged penjing eventually found a home at the National Arboretum alongside a group of bonsai that had just arrived in the United States from Japan.

Every spring, Washingtonians puff up with civic pride as the National Mall’s cherry trees burst into blossom. Tokyo Mayor Yukio Ozaki gave the original cherry trees to the United States in 1912 as a gesture of good will. For the United States’ bicentennial celebration, John Creech, director of the National Arboretum at the time, persuaded the Japanese government to top the cherry blossoms by giving the United States 53 bonsai.

Although West Coast bonsai enthusiasts clamored that the newly acquired trees should be displayed in California—reflecting the Golden State’s pre-eminent role in the history of American bonsai—Creech’s vision of a permanent display of bonsai at the National Arboretum won out. In 1975, arboretum officials broke ground on the museum’s Japanese pavilion. And so the National Bonsai and Penjing Museum took root in D.C.

Today, the largest bonsai in the collection is the 6-foot-tall Imperial Pine, which is one of the original 53 trees from Japan. Several months after arriving in D.C., the Imperial Pine proved its diplomatic savvy: When a local family of robins attempted to nest in its finely groomed canopy, the Imperial Pine obliged; members of the Japanese bonsai community rejoiced, for this was a sign. The trees had been accepted.

Each day, however, visitors to the museum walk by the Imperial Pine and other beautiful bonsai, oblivious to the stories behind them. They pass a Japanese white pine and a persimmon, unaware that the two trees were gifts to President Ronald Reagan from the king of Morocco. They stroll by a grouping of 11 junipers, unsuspecting that each tree represents one of Naka’s grandchildren. (Naka likes to joke that his eldest grandson, who is represented by a tree at the back of the grove, laments his symbolic obscurity in the family.) Worst of all, visitors amble through the museum’s tropical conservatory without knowing that the banyan tree in front of them has made cameos in both The Karate Kid, Part II and an episode of Magnum, P.I.

Near each bonsai and penjing in the museum rests a plaque with the donor’s name, the tree’s age, and the scientific as well as common name of the plant—nothing else. “Too many signs destroy the illusion of the show. We want you to focus on the trees,” says Hill.

The layout of the National Bonsai and Penjing Museum reflects Hill’s less-is-more curatorial approach, subtly illustrating how the art has evolved separately in three regions of the world: China, Japan, and North America. The recent show “Winter Silhouettes,” for example, displayed 13 deciduous bonsai stripped of their leaves by winter. Their twisted branches cast intricate shadows on the white walls behind them. Aside from the shadows, a mere two lines of text accompanied the bonsai. The uncluttered display captured the austere beauty of the season.

Even after five years as a professional curator, Hill occasionally borrows an analogy from the electronics industry to describe his current work. “The art form of bonsai is like the business of cameras,” he says. “You know next year’s cameras are going to be better than this year’s.” The same is true of Hill’s bonsai. On most days, you can find him striving to refine the museum’s collection; even if it’s one leaf at a time, Hill is driven to make the little trees look better.

Jack Cardon, a retired lawyer and volunteer at the museum since 1988, has been working on a prostrate juniper all morning. For hours, he has diligently plucked needles, tucked limbs, and tightened training wires in an effort to re-center the bonsai’s apex above its sinuous trunk.

At the end of the day, he steps back from the tree and takes a long look. Hill joins him. They stare in silence. Hill crosses his arms, tilts his head slightly, and asks Cardon, “Are you happy?”

When you’re working with trees that work on you, happiness, it seems, is as good a gauge of success as any. CP