Eucalyptus in San Francisco’s Urban Forest

One of the arborists who looked at Sutro Forest sent us this article, reprinted with the permission of its author. Written about San Francisco’s Glen Canyon, it was first published in 2009. Alma Hecht was formerly a volunteer with Friends of Glen Canyon.

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In the Canyon By Alma Hecht

October’s rain awakened promise for the canyon’s native plants slumbering through droughty summer. Soon coyote brushes’ creamy sprays and flowering currants’ pink pendants cheer winter mornings. Along the paths and up the hills, blue-gum eucalyptus, Monterey pines and cypresses, buckeyes, coast live oaks, willows, holly-leaf and Catalina cherries hold evening dew, drip from downpours, steam and shimmer when the sun pops out.

Dotting the canyon and punctuating the hillsides, the canyon’s overstory (tallest) trees play an essential role. Originally, San Francisco’s trees grew only in sheltered canyons and along waterways. Probably along Islais Creek in the canyon, the Ramaytush tribe of the Ohlone Indians who lived here transformed the willows’ branches into baskets, harvested the coast live oaks’ acorns, and used the hundreds of understory (lower) plants for food, medicine, cosmetics, and shelter. When the Europeans came, the land was cleared for cattle grazing and later, in the 1850s, Adolf Sutro had blue-gum eucalyptus planted.

Today, blue-gum eucalyptus trees still grow in the canyon where every spring our “celebrity” owl nests and fledges. Throughout the year raptors swoop onto their branches between riding thermals or searching for prey. In places the thick carpet from eucalyptus leaf duff allows only the heartiest exotic invasives, such as Himalayan blackberry and cape ivy, to grow, while in other sites outside our canyon natives, such as toyons and elderberries, flourish.

Blue-gums are controversial trees. San Francisco’s Natural Areas Program has a citywide plan calling for both the removal of healthy — and no replanting of dying — blue-gum eucalyptus. Historically, urban forest modifications have been introduced by controlled measures with new trees planted to replace those removed. However, as it stands today, there is no San Francisco plan for a different species of tall trees to replace the blue-gums. Eucalyptus together with Monterey cypress and pines comprise the backbone trees of the greater San Francisco urban forest. A widely used definition of urban forest developed by Robert W. Miller (1997) is “an integrated, city-wide approach to the planting, care and management of trees in the city to secure multiple environmental and social benefits for urban dwellers.”

Urban forestry was initially developed in North America and now is established worldwide. As open spaces are being developed, urban forests are becoming the major arboricultural component of our landscape. Sadly, in a city that prides itself on beauty, the lack of concern in San Francisco for our urban forest is startling. Despite the efforts of city Urban Forester Carla Short, the Urban Forestry Council, and such other San Francisco nonprofits as Friends of the Urban Forest, complicated politics come into play and contribute to the demise of our necessary and healthy urban forest and ecosystem.

The urban forest is a major capital asset that offers invaluable benefits. Its trees provide us with air to breathe, absorb storm-water runoff, create windbreaks, provide nesting and landing for large birds, offer colors, flowers, forms and textures, screen out harsh scenery, focus the eye, and define spaces. Trees impact our moods and emotions. A healthy urban forest is an integral element of our mental and physical health and contributes to a sense of community pride and ownership that balances the concrete and steel of urban life with the leafy and soft sensibility of nature.

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Alma Hecht is a Certified Arborist and landscape designer. “I design sustainable landscapes that although mostly native are not xenophobic.” She can be contacted at Second Nature Design.

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