The California landscape is dotted with numerous plant species, many of them native, but few have a story as rich and multi-faceted as the eucalyptus tree. Native to Australia, this tree has made California its home over the past century and a half, creating a blend of wonder, economic expectation, and ecological concerns.

The journey of the eucalyptus tree to California dates back to the mid-19th century. Attracted by tales of gold and prosperity, many Australians made their way to the Golden State. Along with them came seeds of the eucalyptus tree, which they believed had great potential value. By the 1870s and 1880s, California was amidst a timber crisis. Native woodlands were diminishing, and the state was in dire need of a rapidly growing timber source. The eucalyptus tree, known for its rapid growth and towering heights, appeared to be a promising solution. Its proponents, believing it would not only serve as an excellent timber source but also act as a windbreak and ornamental plant, began widespread plantations.

While the eucalyptus grew impressively fast, hopes for it being a top-tier lumber source were quickly dashed. Most species planted in California had wood that was prone to warping and splitting upon drying. The enthusiasm surrounding the eucalyptus as a miracle timber tree gradually waned. What was initially perceived as a solution turned out to be more of a decorative element in the landscape rather than an economic boon.

Despite its failure in the lumber industry, the eucalyptus managed to root itself firmly in the Californian soil. Over time, this rapid settler began to pose significant environmental concerns. Eucalyptus trees are thirsty plants. Their deep roots often outcompete native species for water, hindering the growth and survival of native Californian plants and altering the balance of local ecosystems. Furthermore, eucalyptus groves have become a concern for wildfires. Their oil-rich leaves and peeling bark make them exceptionally flammable, amplifying dangers during California’s fire-prone seasons.

While over 700 eucalyptus species exist, only a handful made it to California. The most commonly planted and now dominant species is the blue gum eucalyptus (Eucalyptus globulus). Towering over most trees, the blue gum can reach staggering heights, quickly establishing its dominance in the landscape. Other species like the red gum (Eucalyptus camaldulensis) and the sugar gum (Eucalyptus cladocalyx) have also found their way into California, albeit in smaller numbers. The sugar gum is particularly present around the campus of Stanford University.

By the late 1900s, concerns over the eucalyptus’ impact on native habitats led to movements advocating for their removal. Environmentalists and local residents began to see the tree as an invasive species that hindered the natural balance. Efforts to cut down and manage the eucalyptus population intensified, often clashing with those who had come to admire the tree’s majestic presence and the unique ambiance it provided.

Considered among the thousand-plus established alien vascular plants in California—two-thirds of which originated in Eurasia—Eucalyptus seems relatively benign. Of the 374 species in the genus that have been introduced since the 1850s, only 18 have naturalized, and only one of those, E. globulus, has become a nuisance, and then only at the urban-wildland interface along the fog belt of the central coast and Bay Area, and there only after humans gave it an enormous head start with plantations.

Even in these locations, self-sustaining feral forests have not grown dramatically beyond the boundaries of the original plantings. In the Golden State the blue gum has never been especially invasive; rather, it used to be hugely desirable. Other vegetation imported to California for ornamental purposes has spread far more widely or densely—for example, English ivy, periwinkle, ice plant, and pampas grass. Unlike Saltcedar (Tamarix ramosissima), Tasmanian blue gum is not a true problem plant. It cannot be considered a paradigmatic invader, or even a noteworthy one. The authoritative Encyclopedia of Biological Invasions makes note of the “enigmatic” low invasiveness of eucalypts worldwide—“orders of magnitude less successful as invaders than pines.”

From the perspective of both ecology and fire safety, the blue gum eucalyptus is particularly concerning in California when plantations of a single species have transformed into dense, closed-canopy forests. This issue, though, is confined to a limited number of areas within the fog belt. Even within these regions, the eucalyptus thickets are far from being barren, hostile environments.

That said, a relatively recent event did not cast the tree in good light.

The East Bay firestorm of 1991 was a catastrophic event that claimed 25 lives and rendered thousands homeless. Extensive areas of eucalyptus were consumed by the flames. For 26 years, the East Bay Firestorm firestorm was considered the worst fire in California’s history. It was also America’s most costly fire in the wildland-urban interface (WUI).

“People at the time, I don’t think, associated that with a planted plantation; it was just a eucalyptus forest,” CalPoly botanist Jenn Yost told KQED. “And then when the fire came through — I mean that fire came through so fast and so hot and so many people lost their homes that it was a natural reaction to hate blue gums at that point.”

However, it is again important to point out that the density of trees in the area was unusual and not representative of many other areas where eucalyptus have taken root.

Those opposed to the trees argue that their tendency to shed large quantities of bark exacerbates the fire hazard, and hence, they should be removed. On the other hand, proponents highlight that many of California’s native plants are also prone to burning. The 2018 Camp Fire scorched an area 153,336 acres in size, and destroyed more than 18,000 structures, most of the destruction happened within the first four hours of the fire and most of the destruction was the result of pine forests that have long been improperly managed. Both factions claim that science supports their viewpoint, but as of now, no definitive study has been able to settle the argument conclusively.

This ongoing debate has stirred deep emotions. A few years ago, an incident in the East Bay hills saw federal funding for cutting down trees withdrawn after protesters, in a dramatic display of support for the eucalyptus, got naked and literally embraced the trees on the Cal campus. While some have argued that California needs to return its natural environment to a more “pristine” state, meaning just California natives, others say that the eucalyptus poses no greater danger than many species of conifer, and that the effort to expunge eucalyptus from the landscape, given its contribution to the culture and beautification of the state is tantamount to discrimination against immigrant trees solely due to their origin, an idea which some have extended to the human population.

“We’re not natives either,” the San Diego County chief entomologist said in defense of the county’s signature tree genus.

One ecological study that compared a gathering of oaks to a blue gum grove in the neighboring areas, concluded that the blue gem eucalyptus has no major impact on animal life. In fact, the tree’s leaf litter is bustling with life, containing a complex array of microhabitats. In fact, while oaks tend to be home to more rodents, eucalyptus contains a greater number of below-ground invertebrates.

The complex relationship between Californians and the eucalyptus reflects deeper questions about nature, risk, and our connection to the landscape, and it’s a debate that shows no signs of resolution.

Among the thousand-plus non-native vascular plants that have made their home in California—two-thirds of which hail from Eurasia—the Eucalyptus is relatively mild-mannered. Since the 1850s, 374 species of Eucalyptus have been introduced to the state. Yet, of these, only 18 have successfully naturalized, and merely one, the E. globulus, has ever become problematic. This issue is isolated mainly to the WUI boundary along the fog belt of the central coast and Bay Area, and even there, only after humans heavily promoted its growth through plantation efforts.

Even within these specific regions, the self-sustaining “feral” forests haven’t expanded significantly beyond the original planting sites. In California, the blue gum eucalyptus has never been notorious for being particularly invasive; rather, it was once highly sought-after. Other non-native plants brought to California for decorative purposes, such as periwinkle, English ivy, ice plant, pampas grass, and tamarisk, have spread much more extensively or densely.

Unlike plants like Scotch and French broom, the Tasmanian blue gum eucalyptus doesn’t qualify as a genuine problem plant. It’s not viewed as a typical invader, nor is it even considered particularly noteworthy in that regard. A state survey that consulted floricultural experts produced a broad spectrum of opinions concerning the potential threat posed by eucalyptus to California’s wildlands. This contrasts sharply with the unified negative evaluation of salt cedar, which has bedeviled land managers from Southern California to Mexico.

The final verdict on the fate of eucalyptus in Southern California has yet to be rendered. Many still think the trees have become an iconic symbol of the state, with so many trees proudly and elegantly lining pocketed and immensely Instagrammable stretches of California highway. Perhaps the key to the trees survivability and reputation is simply one of proper management. Where the trees have become too dense in fire-prone areas, maybe some measure of thinning is prudent. But to eliminate them entirely would be a great loss to the aesthetic visual appeal of California, an appeal that many Californians, even conservation-minded artists like Ansel Adams and Erin Hanson often summoned in their work.

The eucalyptus tree’s journey in California is a tale of expectations, surprises, and evolving perspectives. Whether viewed as an ornamental marvel or an ecological concern, the eucalyptus remains an integral part of California’s diverse tapestry.