Corymbia is a genus of around 100 trees native primarily to Australia, with a few native to New Guinea as well. Like their better known cousins, Eucalyptus, they belong to the family Myrtaceae. In fact, until the 90's these trees were considered to be just one of many branches of that genus. Modern genetics work has shown they are distinct, and so they were separated. However, most people will be hard pressed to tell these two closely related genuses apart, and refer to all of them as Eucalyptus. To be technically correct when you are uncertain, the terms eucalypt or gum tree can be used.
I have observed three species of Corymbia in the Sacramento area, but none are common. C. ficifolia, the red-flowering gum, is maybe the most famous Corymbia in Northern California. It is a popular tree in San Francisco but is rarely grown in inland areas. The single scraggly individual I have seen in Capitol Park is not a promising example, but it is alive. C. citriodora, the lemon-scented gum, is more commonly seen in Southern California. This species is famous for the odor of the leaves, from which citronella is derived. I have seen a few in Sacramento where they grow rapidly to a remarkably tall and slender form. Both are marginal in terms of hardiness, not sustaining damage in the average year but in danger if temperatures drop below the mid twenties. The last species, C. apperrerinja, or ghost gum, is not yet well known but was trialed in the Climate Ready Tree experiment run by UC Davis and the US Forest Service. It shows promise as a drought tolerant and fully cold hardy species, though many trees in the study succumbed to phytophthora.
Corymbia share many of the pros and cons of Eucalyptus, but have an undeniable beauty that is all their own. I suspect they may have a role to play in our urban forest, but more testing is needed to identify the right species for the local climate.
I have observed three species of Corymbia in the Sacramento area, but none are common. C. ficifolia, the red-flowering gum, is maybe the most famous Corymbia in Northern California. It is a popular tree in San Francisco but is rarely grown in inland areas. The single scraggly individual I have seen in Capitol Park is not a promising example, but it is alive. C. citriodora, the lemon-scented gum, is more commonly seen in Southern California. This species is famous for the odor of the leaves, from which citronella is derived. I have seen a few in Sacramento where they grow rapidly to a remarkably tall and slender form. Both are marginal in terms of hardiness, not sustaining damage in the average year but in danger if temperatures drop below the mid twenties. The last species, C. apperrerinja, or ghost gum, is not yet well known but was trialed in the Climate Ready Tree experiment run by UC Davis and the US Forest Service. It shows promise as a drought tolerant and fully cold hardy species, though many trees in the study succumbed to phytophthora.
Corymbia share many of the pros and cons of Eucalyptus, but have an undeniable beauty that is all their own. I suspect they may have a role to play in our urban forest, but more testing is needed to identify the right species for the local climate.