The first ones were planted in California in 1856, according to the Sunset Western Garden Book. The word eucalyptus comes from the Greek eu, good, and kalypto, to cover -- as in a lid. This refers to the septals and petals in each tree, which fuse into a cap that falls off when the flower opens. Good-cover aptly describes what eucalyptus have been used for in the West. They grow everywhere, even if no one told them to. They were brought here for railroad ties, and failing that, they flourished. Over 50 species are listed in the Sunset book, and Elizabeth MacPhail's book on Kate Sessions ( Pioneer Horticulturist) gives the mother of San Diego horticulture credit for popularizing a dozen different species. Local eucalyptus trees range from great beauties to filthy beasts. Any way you look at it, there's way too many of them.
A couple of years back I knew a big old cladocalyx (sugar gum) patriarch in Old Town State Park that once gave up a limb large enough to wipe out a group of European tourists. The tree dropped its load in the early morning, scaring nobody but the feral cats and gray bunnies that take over the place while we sleep. Less than six months after the limb dropped, a horde of tree-trimmers were out there armed with chainsaws and snorkel lifts; like a bunch of gas-powered beavers on stilts, they chopped the crap out of the tree.
Eucalyptus is frigging everywhere in malevolent glory; our climate is a steroid tonic for most species. Landscape architects from down under are astounded by the size and scope of their brethren here; as exotics in California, the trees do stuff they'd never dare back home. Species of Eucs that would be in scrubby little mallees in Australia become hulking brutes here.
Until recently, there were no predators to weaken the Australian transplants. But the eucalyptus longhorn beetle got a visa in 1984 and began boring away. The beetle became so successful that citizens of Rancho Santa Fe hired entomologists to bring in a hired killer from Australia (a wasp) to lessen the destruction. (Unfortunately, it's not working.)
People love eucalyptus trees; they're the most widely planted non-native trees in California and Arizona. Here in San Diego, they form the top of the floral canopy, infecting the skyline, barely leaving room for the occasional tall palm or fellow Aussies like melaleuca (they're like giant bottlebrush trees). Blue gums (E. globulus) will do 100 feet; Manna gums (E. viminalis ) will clear 100 feet; cladocalyx are in the 100-foot range. I like the damn things, but I think there's room in this city for botanical diversity.
Other species of tree are represented throughout the county: liquidambar, jacarandas, magnolias, pines, cedars, ficus, peppers, corals, ashes, alders, olives, pittosporums, poplars, willows, boxes, and that hideous in-betweener, the cypress/juniper, which sprouts like a giant green phallus. Almost anything will grow in San Diego, and therefore almost everything does. But we have our favorites. The popular ones are that way because they make swell fences and require little attention.
If there's a single plant that'll send me over the edge, it's oleander. No good reason for a Nerium oleander in every third yard in San Diego, but look around and you'll find one. They're one of the dominant flowering plants visible as you drive the canyons. Come down the grade on I-15 from Escondido to North County Fair, and they form a flowering wall between the northbound and southbound lanes. Drive down San Diego Avenue or walk through the state park, and you'll see them turned into flowering trees. There's an impressive group along the eastern shoulder of 805 north, from Balboa up to 52. People like them so much that horticulturists developed a dwarf version.
If you're looking for cheap botanical thrills, oleanders have many desirable qualities. They're tolerant of almost anything -- heat, drought, bugs, bad soil, bad care, savage pruning (Caltrans must beat the oleanders on I-15 into submission with a mutant lawnmower), fire, earthquake, pestilence.... They're cheap, and they have flowers that come in white, red, pink, and shades in between. Oh yeah, they're poisonous, too. I remember when my father warned me about oleander toxicity with a story about a little girl who died after she ate the pretty pink flowers. He told me with disdain in his voice, like, "Don't be stupid and eat shit that you know nothing about." He'd found out I liked to eat the berries off the Catalina cherry bush, and he feared I'd go for oleanders next.
We've become so habituated to certain plants that we can't see them anymore. Palms are like that; they don't stand out because they've been stereotyped by regularity. We crop them, cut their gray frond skirts off so we can see their naked trunks. Unlike the Victorians, who were known for covering piano legs with fabric because it was considered risqué to leave legs (inanimate or not) uncovered, we like to expose the trunks of our Mexican fan palms. Some would say it's because vermin live in the fronds, but I'd bet it has more to do with the South Pacific and our desire to be around coconut palms. Coconut palms don't grow well here -- too cold in winter -- so we turn Washingtonia robusta into a fruitless equivalent.
The San Diego Historical Society houses a set of photographs that occupy the back wall of their research archives. The series marks the beginning of the palm era, giving a visual lesson in downtown's landscape history. I spent an afternoon trying to figure out when a specific palm, a Canary Island palm ( Phoenix canariensis), was planted and by whom. The photos, blown up to several feet, show a view of downtown looking across Beech and Ash streets and Sixth and Seventh avenues. The first picture is from 1873, then one in 1888, 1904, 1929, 1972, and one from 1990. According to the photos, the palm was planted sometime between 1888 and 1904 at what is now 620 A Street. And it's still there, only now, instead of standing proudly alone in front of the ginger cottage, it's surrounded by surly office buildings.