Presidio's Historic Forest Stands Tall on Arbor Day

​​​​​Presidio of San Francisco (April 21, 2009) — This Friday, April 24, as the country celebrates Arbor Day, the Presidio forest will celebrate its 123rd birthday. The historic forest is one of the Presidio’s defining features. In fact it would be hard to imagine the park without its 300 acres of eucalyptus, pine and cypress.

The forest is the most dramatic example of how people shaped the Presidio’s landscape. Its 60,000 trees provide an important wildlife habitat (the forest is home to more than 250 different species of birds) and contribute to the Presidio’s National Historic Landmark status.

In the late 1800’s the Army began the prodigious task of transforming the Presidio from mostly open dunes to a richly forested, park-like reserve, similar to New York’s Central Park. Following a plan developed by Major William A. Jones, the Army planted some 100,000 trees over 14 years along the Presidio’s ridges and entrance gates. The first trees, donated by Adolph Sutro, were planted in 1886, on Arbor Day. The eucalyptus, pine and cypress groves accentuated the post’s size, sheltered it from the winds and created a clear visual distinction from the surrounding city. It was the Army’s most impressive accomplishment in landscape architecture. No other military installation in the nation has ever undertaken landscape planning on such a grand scale.

The relatively short period of time during which the trees were planted however, created an “even-aged” forest. And while the eucalyptus have thrived, the cypress and pine have begun declining simultaneously. Presidio forester Peter Ehrlich is leading an ambitious effort to revitalize the forest over the next several decades.

“The goal,” says Ehrlich, “is to create an ‘uneven-aged’ forest that can be more easily sustained and will be a healthier forest in the long run.”

Each year the Trust replants two to three acres of pine and cypress. Since 2002, more than 2000 trees have been planted, with a careful eye says Ehrlich “towards preserving the qualities that define the forest’s character, like the orderly, military alignment of the trees.”

Staying one step ahead of nature is as Ehrlich puts it, “a daunting challenge.” One he has, at times, met with the latest scientific methods. Several years ago, in the face of an outbreak of pitch canker disease among Presidio pines, Ehrlich and his staff, along with foresters from U.C. Davis identified, then cloned Presidio pines that showed resistance to the disease. In 2004, more than 140 of the experimental, disease-resistant trees were planted. Five years later they appear to be thriving.

Current efforts are focused on finding a less aggressive and invasive replacement for the Tasmanian blue gum, a eucalyptus tree that can live to be 300 years old and is the most populous tree in the Presidio. The new tree Ehrlich says would look the same as a blue gum and be the same height, “only without the aggressiveness.”

Ehrlich came to the Presidio in 2000, after serving as the city of San Francisco’s urban forester, a role in which he oversaw the care of trees in Golden Gate Park as well as all the city’s neighborhood parks, golf courses and open spaces.

“Hopefully people will enjoy watching the growth of the new forest,” Ehrlich says. “And through our education efforts we can create a better understanding that what we’re doing is best for sustaining the long-term health of the forest.”

For more information on the Presidio Trust’s reforestation efforts visit: Creating a Sustainable Forest.

The Presidio Trust was established by the United States Congress in 1996 to oversee the Presidio of San Francisco, an urban national park located at the base of the Golden Gate Bridge. The 1,500-acre site contains expansive open space and spectacular views, a 300-acre historic forest, and rare and endangered plants and wildlife. It also comprises nearly 6 million square feet of buildings, including 469 historic structures that contribute to its status as a National Historic Landmark District.