COVELO - After 500 years or more, the monumental valley oak in Round Valley has grown into the largest specimen of its kind in the United States.
The Henley tree's base is so big it would take 20 people standing shoulder to shoulder to encircle it.
"It's a magnificent oak specimen," said Steve Sillett, a Humboldt State University tree expert.
Sillett leads a university research team that takes official measurements of the biggest trees around the globe, including the tallest - a towering redwood in Humboldt State Redwood Park.
The 140-foot-tall Covelo tree, as it is also known, has been recognized among a small circle of experts as the nation's champion oak since the 1980s. A recent examination by Sillett confirmed it's still the largest despite the ravages of age and high winds.
The valley oak, which grows only in California, is the largest species of North American oaks. Typically, valley oaks grow to 30 to 75 feet tall and 3 to 7 feet in diameter.
According to the National Register of Big Trees, a list put out by the conservation organization American Forests, the Henley oak is the largest tree of any oak species in the country.
Sillett said the giant may live another century or two, given an almost perfect marriage of soil and climate: "The conditions are ideal."
The tree towers above other valley oaks scattered across a 7,000-acre cattle ranch owned by Sheila and Bobby Fetzer, members of Mendocino County's best-known winemaking family. The tree grows near a restored barn just east of Highway 162 at the southern end of Round Valley in northeastern Mendocino County.
The secluded valley is a spectacularly beautiful place. Snow-covered mountains ring the valley this time of year. It also is home to the state's largest Indian reservation. The valley population of about 3,000 is almost equally divided between the local Indian tribes and white residents.