Acacia

🇺🇸 History in the United States

A few acacia relatives (such as catclaw acacia) are native to the American Southwest, but the acacias that matter most for US allergy sufferers are Australian species imported to California during the horticultural boom that followed the Gold Rush era of the mid-1800s. Nurserymen introduced silver wattle (Acacia dealbata), Sydney golden wattle (A. longifolia), and blackwood acacia (A. melanoxylon) as landscape ornamentals, street trees, windbreaks, and timber trees, and poet-naturalist Joaquin Miller famously planted acacias in the Oakland hills at the end of the 19th century. The trees thrived in California's Mediterranean climate and by the 20th century several species had escaped cultivation and naturalized along the coast, with blackwood and silver wattle now listed as invasive by the California Invasive Plant Council. Because acacias bloom conspicuously in February and March, they were historically blamed for winter hay fever, and acacia pollen extracts entered US allergy testing panels in the 20th century. Modern aerobiology has tempered that reputation: acacias are largely insect-pollinated with heavy pollen that travels poorly, so they are considered only mildly allergenic and important mainly near the trees themselves. They remain fixtures of California and Gulf Coast landscaping, and related wattles such as black wattle have been profiled as allergens of note in the allergy literature.