Eucalyptus is a genus of evergreen trees native almost exclusively to Australia, yet it has become a prominent fixture in the landscape of the United States. These fast-growing trees were introduced for a variety of commercial and ornamental purposes. The distribution of eucalyptus in the US reveals a highly concentrated presence in the West, with smaller, specialized pockets of growth elsewhere. The geographic range of these non-native trees is a direct reflection of regions that successfully mimic the mild, temperate conditions of their homeland.
The Dominant Presence in the Western US
The largest and most historically significant concentration of eucalyptus in the United States is found along the West Coast, particularly in California. Plantings began in 1853, driven by the need for timber and fuel during the Gold Rush era and later by land developers. The state’s Mediterranean-like climate, characterized by mild, wet winters and hot, dry summers, proved highly amenable to the species.
The blue gum (Eucalyptus globulus) thrives along the coastal and southern California regions. A major planting boom occurred between the 1870s and 1910s, with millions of trees planted across the state for potential use as railroad ties. While this commercial venture ultimately failed due to the wood’s tendency to twist and crack upon drying, the resulting trees remain a defining feature of the landscape.
Beyond California, the eucalyptus presence extends into the mild, coastal stretches of Oregon and Washington where winter temperatures rarely fall below freezing. Arizona also sees limited cultivation, primarily in warmer, lower-elevation areas. However, these states do not host the extensive, large-scale groves that characterize the historical plantings of California.
Critical Climate Factors for Eucalyptus Growth
The distribution of eucalyptus in the US is fundamentally restricted by its low tolerance for cold temperatures and frost. Most commonly cultivated varieties, such as the blue gum, require a minimum USDA Plant Hardiness Zone of 9, where the average annual minimum temperature does not drop below 20°F.
A brief exposure to temperatures below 20°F can cause significant damage to the foliage and younger branches, while prolonged freezing can kill an entire tree. Eucalyptus also generally requires well-draining soil to prevent root rot, though some species are adapted to wetter conditions. Their ability to tolerate drought, especially older, established trees, makes them suited to regions with distinct dry seasons.
Secondary and Specialized Growth Regions
Outside of the West Coast, eucalyptus cultivation is limited to specialized regions that offer thermal protection. Hawaii is a significant growth area, where the tropical climate allows many species to flourish, including Eucalyptus robusta (Swamp Mahogany) and Eucalyptus deglupta (Rainbow Eucalyptus). These species have become naturalized in some areas.
The Southeast US, specifically central and southern Florida, also supports eucalyptus growth due to its subtropical climate. Species like E. grandis and the cold-hardy E. benthamii are successfully grown in commercial plantations for pulpwood and mulchwood. Along the Gulf Coast of Texas and Louisiana, certain cold-hardy varieties, such as Eucalyptus gunnii and Eucalyptus neglecta, are cultivated, but their presence remains primarily ornamental and less extensive than the dominant groves in California.