Most of us know eucalyptus as an ingredient in balms, lotions, or potpourri, or as an aromatic addition to flower arrangements or dried plant bouquets.

https://en.wikipedia.org/wiki/Eucalyptus

This rapid-growth tree is not native to the US but was imported from its native Australia and quickly became established in California.

Because the eucalyptus can reach great heights in a short period of time, and because it loves the climate of California, the tree was widely planted.

Alas, the eucalyptus became a danger to indigenous plants – and the oils that made the plant useful became an explosive nightmare when forest fires erupted.

https://www.kqed.org/news/11644927/eucalyptus-how-californias-most-hated-tree-took-root-2

This postcard photograph was made while Californians still had great enthusiasm for the tree,

Published by the Souvenir Publishing Company of Los Angeles and San Francisco, the postcard was probably printed in the United States.

The postcard was not mailed; it may have been collected by one of the many visitors to California.