It's the dead of winter, but the Southland's urban forest knows no season. Skyduster palms sway in the breeze. Sprawling Indian laurel figs shade sidewalks. The broad leaves of Southern magnolias soak up the January sun.

How did Los Angeles become an evergreen city? Aqueducts mean these trees won't soon thirst for water in the Southland's semiarid climate. But the region's urban forest also owes its existence to a generation of agricultural innovators, amateur gardeners, nursery operators, and others who brought trees from exotic locales like Australia or the Andes to improve -- to "emparadise" -- a landscape they found lacking.

In his magnificent new book, "Trees in Paradise: A California History," environmental historian Jared Farmer tells the story of this landscape revolution -- among many others. For example: California's vegetable giants inspired awe around the world, but the state nearly reduced the entirety of its vast coast redwood forest to stumps. Also: immigrant labor sustained Southern California's Orange Belt, yet it was rarely acknowledged in the idyllic scenes created for picture postcards and citrus crate labels.

I asked Farmer to elaborate on some of the themes he raises in his book. Images from L.A. as Subject member archives accompany our conversation, which you can read below.

This postcard manages to include three of the four tree types covered in Jared Farmer's book, 'Trees in Paradise': eucalypts , oranges, and palms. Courtesy of Jared Farmer.

Nathan Masters: Much of the action in the first part of your book, about California's two redwood species, takes place far north of Southern California. How is the Los Angeles area connected to these trees' stories?

Jared Farmer: My story of giant sequoia is primarily about how the Big Trees entered national and international consciousness, and I write more about New York and London than Los Angeles. With the coast redwood old-growth forest, however, Southern California is very much implicated in the story of its liquidation. For example, the original bleachers at the Rose Bowl -- 28 linear miles -- were made of coast redwood. Pasadena's famous Craftsman bungalows were, too. To get from San Diego to Yuma, early motorists crossed the forbidding Algodones Dunes on a redwood plank road (a forerunner of I-8). All over the Golden State, people drew water from redwood tanks and pipes, and buried their dead in redwood caskets. From the late nineteenth through the mid twentieth century, Californians used redwood for almost everything: harbor piles, railroad ties, telephone poles, tanning vats, shingles, fence posts, boxes, pencils -- you name it. Indeed, until 1914, when the North Coast finally gained a direct rail connection to the transcontinentals and when the Panama Canal opened, redwood lumber was essentially an all-California resource, made and used and wasted at home. Even after 1914, Californians used the bulk of the resource. At the Port of Los Angeles, oil and oranges went out by barge; redwood lumber came in. The Southern California dream of homeownership was framed and finished with heartwood from one of the mightiest forests in world history.

Four bonneted campers with a giant sequoia tree named after Los Angeles in Yosemite's Mariposa Grove, circa 1900. Courtesy of the USC Libraries - California Historical Society Collection.

NM: You're fond of sharing two poems about eucalyptus, one vilifying the tree and the other praising it. What's the final verdict -- where do you stand?

JF: Yeah, I love the fact that Robinson Jeffers wrote a sonnet in praise of eucalyptus: I love it when the past surprises us and compels us to investigate the origin of things. The millions of eucalypts you see throughout the Golden State did not result from bioinvasion; they originated with human desire. Californians of earlier generations wanted these trees. Today, we are the caretakers of their horticultural choices. I'm puzzled that the debate on California eucs has for some three decades been stuck in good-or-evil polemics when there's actually a lot of room for middle ground. As I wrote in a recent op-ed, it matters less where the trees came from originally than how they fit in now. From this point of view, eucalyptus belongs in some parts of California and not in others. Context means everything.

Two men demonstrate the girth of a 25-year-old blue gum tree on the L. J. Rose ranch in Rosemead, circa 1900. Courtesy of the USC Libraries - California Historical Society Collection.

NM: Almost all of California's human inhabitants are immigrants to the state, in one way or another. So are most of its trees. Are these two statements related?

JF: Absolutely. The most cosmopolitan U.S. state has the most varied flora. That's not a coincidence. Immigrants from all corners of the globe have here tried growing anything and everything -- including trees from their places of origin. Of course, it helps that lowland California -- more than any other North American region -- has a climate suitable for a wide variety of temperate, Mediterranean, and sub-tropical plants.

NM: So has the fact that so many "immigrant trees" populate California's landscapes influenced cultural attitudes toward human immigrants? Or is it the reverse?

JF: These issues don't line up in the past the way you might expect. In U.S. history, at least, botanical xenophobia and actual xenophobia have rarely occurred together. Many leading conservationists of the late nineteenth and early twentieth centuries were in fact racists, nativists, and even eugenicists, but these people supported plant introductions more often than they opposed them. I'll give you an example. Abbot Kinney, one of the principal promoters of eucalyptus planting (and founder of Venice and the namesake of Kinney Boulevard), wrote a book in 1893 about the "religion of reproduction." In it he argued for the spiritual calling and the civic duty of procreative sex. Educated married couples of "native American stock" -- by which he meant white people -- needed to reject contraception lest their race go extinct, and lest the nation be overrun with the illiterate children of hyperreligious immigrants of undesirable races. Yet Kinney, despite his horticultural interests, did not draw any analogies to the plant kingdom; he passed up the easy rhetorical move to liken immigrants to weeds. Inversely, when Californians initially turned against eucalyptus trees in the 1880s, they did not compare unwanted specimens to despised foreigners such as the Chinese. (And during the two world wars, jingoistic Americans failed to call for a war on German ivy or for the removal of the Japanese cherry trees from the National Mall.)

NM: Your book explores four types of trees: redwoods, citrus, eucalypts, and palms. If you'd found room for a fifth tree, what would it be?

JF: I'm pretty sure my editor would have balked at a proposed fifth section! Besides, I was able to cover almost everything I wanted to cover with these four types: native and non-native species; wild and agricultural and ornamental and symbolic plants; trees in Southern California, the north, the Central Valley, the coast, and the desert; trees on private and public land; trees in wilderness areas, nature parks, urban streets, suburban yards, and corporate farms.

So for me the question becomes, "Should I have substituted another type for one of my four?" For my agricultural tree, I suppose I could have used the state's current number-one commercial tree, almond, or another one of the historically important tree crops such as olives or apricots, but honestly nothing matches the former economic and symbolic importance of citrus. My only second-guessing concerns oak trees. My rationale (rationalization?) for excluding oaks -- California's quintessential indigenous tree type, and the one with the deepest history with the greatest number of native peoples -- was that I could explore the theme of indigeneity through the negative example of eucalyptus, the state's most famous non-native tree. Since I was committed to starting my story in 1848, the year the U.S. vanquished Mexico and the year Americans discovered gold, I stand by my choice of eucalyptus, which was introduced in the early 1850s. However, had I written a book that started in 1769 (the founding of California's first mission) or earlier, I certainly would have chosen oaks instead of eucs. I'm afraid that writing any book, even a long one like mine, is more about omission than inclusion. If you accept Philip Fradkin's division of California into "seven states," my book slights two of them: the lava country of the northeast (Fradkin's "Land of Fire") and the Mojave Desert (including its iconic Joshua trees). You just can't do everything!

A coast live oak stands in the middle of Pasadena's Orange Grove Avenue. Courtesy of the Security Pacific National Bank Collection - Los Angeles Public Library.

NM: How did palms become such a potent symbol of L.A.? And when you look into the future, do you see their iconic status eroding away, much as pepper trees lost theirs?

JF: You're right: A century ago, the iconic street tree of Los Angeles was not any kind of palm, but the pepper tree (Schinus molle), a species of sumac native to the arid zone of South America, with its distinctive feathery foliage and scarlet berries. This tree served as Southern California's answer to the weeping willow. On my book's Facebook page, I've posted vintage postcards and greeting cards that just show just how emblematic pepper trees used to be. Today, I bet most Angelenos wouldn't be able to pick one out from a line-up of trees. (If you want to get a sense of what the L.A. treescape once looked like, drive around Rancho Palos Verdes and Rolling Hills Estates, which still have splendid peppers.)

Palms replaced peppers in the built environment and the psychic landscape of L.A. for a few reasons. First, many of the pioneer pepper trees were torn out in the early twentieth century because they acted as a reservoir for black scale, an insect that damaged citrus groves. In 1930 Los Angeles followed the example of the citrus colonies and banned further street planting of the species.

Circa 1930 postcard showing a banana palm (not technically palm tree) next to a pepper tree in Los Angeles' Pershing Square. Courtesy of the Werner Von Boltenstern Postcard Collection, Department of Archives and Special Collections, Loyola Marymount University Library.

Meanwhile, in the 1920s and 1930s, L.A. was busy building its modern grid of automobile boulevards, and the city's newly established Division of Forestry was looking for standardized street trees. In advance of hosting the Tenth Olympiad in 1932, City Hall announced a 10-year plan -- a Depression-relief works project -- to set thousands of trees along major boulevards. Metropolitan foresters chose not to reproduce the familiar street trees from the pioneer era -- acacias, eucalypts, and peppers. In the age of streetside parking, sidewalks, sewers, and utility poles, these leafy, rooty growers acquired bad reputations. In contrast, palms held out the promise of symbiotic infrastructure: they could provide beautification without dropping fruit, buckling concrete, or breaking pipes and wires.

The species planted most prevalently by city crews was Mexican fan palm (Washingtonia robusta), native to Sonora and Baja. City officials probably had no inkling these seedlings would grow so tall. The species wasn't singled out for aesthetics. Rather, it was hardy and it was cheap.

Prior to the mid twentieth century, when these uniform rows of Mexican fan palms reached maturity, fronds were not a leading feature of the urban landscape, despite the fact that tourism boosters had incessantly advertised the palminess of Greater Los Angeles. The most visible species was Canary Island date palm (Phoenix canariensis), which wealthy homeowners habitually planted in pairs along their front walkways. Although San Diego, Santa Barbara, Redlands -- and even Sacramento -- were decades ahead of Los Angeles in cultivating a palmy landscape, L.A. had better boosters. "We used to go down to the Capitol Theater in Sioux City, Iowa, and sit there and watch Bing Crosby movies," recalled one transplant, "and I said, 'Man, is that what it's like out there? I got to get out there!' See how naive we were. Why, hey. They could paint those palm trees in the back of those movie sets as fast as you could leave."

This avenue of Mexican fan palms, the earliest of its kind in Los Angeles, was planted in the 1870s, and was famous as a curiosity in the pre-automobile era. Seen here in 1930, the avenue is now part of the Orthopaedic Hospital complex near Adams Blvd and Flower St. Courtesy of the USC Libraries - Dick Whittington Photography Collection.

Thanks to the entertainment industry, Mexican fan palms acquired associations with sex, glamour, and celebrity. As it happened, the city's roadside plantings achieved spectacular heights in the same era that Hollywood became a dominant force in global entertainment. All of those thousands of films and TV shows shot outdoors in postwar Los Angeles cemented an association in people's minds: tall, skinny palms = L.A. Mexican fan palms became the icon of verticality in the postwar metropolis, complementing the freeway, the icon of horizontality.

The city won't lack for palms any time soon. However, the era of the "skyduster" Mexican fan palm will end later this century as the even-age cohort of street trees passes away. Since fan palms don't provide adequate "ecosystem services" such as shade, city councilors approved a policy in 2006 not to replace them -- with exemptions given to Hollywood and Sunset boulevards. The city prefers queen palm (Syagrus romanzoffiana), a feather palm that grows more densely and compactly. Over time, then, L.A's skyline will become less distinctive, with fewer and fewer bundles of fronds floating high above the freeways catching the last warm light of the setting sun. Fifty years from now, the tallest palms in Southern California will be in Orange County and the Inland Empire. Film crews may have to go there to get their "L.A." establishing shots. Or they may just digitally add some high-rise palms.

NM: Whenever the subject of trees in Southern California comes up, I'm always asked about jacarandas. In your research, did you find any satisfying explanations for how they became such a distinctive part of the region's arboreal landscape?

JF: I didn't do any focused research on jacaranda trees, but here's what I learned in passing. The species commonly seen in Southern California, Jacaranda mimosifolia, native to South America, was championed by Kate Sessions, the great landscaper of San Diego and mother of Balboa Park. Before her, jacarandas showed up on the species lists of societies representing the acclimatization movement -- a nineteenth-century global effort, parallel to European imperialism, to "scientifically" introduce desirable species to favorable environments. Acclimatizers wanted to increase what we would now call local biodiversity, and they had no compunctions about using non-native species. Jacarandas became popular in Australia as well as California, one more example of the arboreal and aesthetic connections across the Pacific (a topic examined by historians Erika Esau and Ian Tyrrell). The California capital of the acclimatization movement, Santa Barbara, boasted of its jacaranda, also called "Green-Ebony." The plant also became fashionable in the colonies of the Citrus Belt from Pasadena to Redlands, in part because it looked spectacular in bloom and in part because it didn't harbor scale insects that hurt orange trees. The citrus colonies -- among the wealthiest and most beautifully landscaped places in America in their heyday -- set the regional fashion trends in trees far more than Los Angeles. Charles Saunders, the prolific nature and garden writer from Pasadena, commented in 1916 that driving Foothill Boulevard (the precursor of the 210 freeway) "is nothing short of entrancing" in early June "when the jacaranda trees are a cloud of blue." (By the way, I haven't seen it, but one of final episodes of California's Gold by the late Huell Howser took up the question whether jacarandas are a "mess" or a "miracle.")



NM: You're on the East Coast now, but if you lived in Southern California, what trees would you plant in your garden?

JF: With climate change, it's only going to get hotter and drier here, so I'd look for drought tolerant species. Since I have a soft spot for Australasian trees, I might be tempted to plant a flowering acacia. But each garden has different needs and constraints. For guidance on picking the right tree for the right spot, Californians can consult a great website managed by the Urban Forest Ecosystems Institute at Cal Poly San Luis Obispo. With some obvious exceptions (species that are thirsty, rooty, messy, invasive, prone to disease, etc.), the more trees the better in the urban Southland. They cool and filter the city's air, among other benefits. The same is not true for lawns -- a water-intensive English landscape tradition that should be abandoned in Southern California except for special-use zones like playing fields. My garden would be proudly lawn-free. If I had enough room, I'd love to plant a native coast live oak (Quercus agrifolia). True, I might not live long enough to see it grow to full size, but someone else would. Like the Chinese proverb says, "The best time to plant a tree was twenty years ago; the second best time is today."

NM: One last question -- do you have a favorite individual tree south of the Tehachapi?

JF: I have a couple of favorites, one wild, one planted. The former is a grand specimen of big-cone pine (Pinus coulteri) that grows at the bend of a trail I've hiked many times above Big Tujunga Canyon in the San Gabriels. The latter is an entwined pair of lemon-scented gums (Eucalyptus citriodora) that towers over Henry E. Huntington's mausoleum on a hillock above the last remaining orange grove in Los Angeles County. Despite losing some major branches in the big Santa Ana windstorm of 2011, these sculptural, smooth-barked eucalypts remain magnificent.