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The eucalyptus: our signature tree

Many eucalyptus trees were originally planted for E.W. Scripps’ Ranch. (photo by Heather Karpel)

The eucalyptus: our signature tree

The seeds that brought California the eucalyptus tree traveled a long way to get here. They were shipped across the Pacific Ocean from Australia around the time of the California gold rush in the 19th century. The idea was to use them for railway ties. Unfortunately, the eucalyptus’ incredible growth rates made for wood that cracked and was not useable. Today, eucalyptus trees tower above others in the area, and they are numerous in Scripps Ranch.

David Ehrlinger served as the director of horticulture at San Diego Botanic Gardens for 12 years. It was on a trip to the West Coast in 1970 that Ehrlinger decided horticulture was his calling, and the eucalyptus tree had a lot to do with it.

“I stayed with a friend for several weeks and was just dazzled by these eucalyptus trees and how tall they were,” Ehrlinger said. “The large eucalyptus seemed to be 25 percent taller than the tallest trees back east. They are just an extraordinary arboreal phenomenon.”

Ehrlinger said that many of the large eucalyptus trees of Scripps Ranch were originally planted for E.W. Scripps’ ranch. The trees tend to fare better in canyons than on slopes, because water drains into canyons. Eucalyptus trees are well known for their fragrant leaves. Three of the more common eucalyptus in California are the blue gum, the red gum and the skyline, or sugar gum. Ehrlinger explained that the red gum, which is common in Southern California, is “quite a tree” and “adapts to a variety of soils and all kinds of climatic conditions.” It thrives in the low-moisture conditions of Southern California and Australia, and at the other extreme, he has seen photos of the tree growing in swamps.

The skyline gum, which is also common in this area, can grow to be over 100 feet in the right soil and with enough moisture.

“It’s way too big of a tree for your yard, but off on the hillside, they’re just beautiful, iconic trees,” Ehrlinger said.

The eucalyptus has been criticized for being a fire hazard. It gained this reputation in part because of its high oil-containing foliage. Other factors have to do with the conditions that have begun to affect it — prolonged years of drought and pests. One of the reasons the tree grew so successfully here is because, as a non-native species, it had no natural pests. In the 1980s new pests were introduced into the area and they began to attack the eucalyptus. Sick trees tend to drop more branches and leaves than healthy ones.

“The most flammable aspects of eucalyptus trees are the dead foliage and bark on the ground, along with fallen branches and twigs,” Ehrlinger said. “These can create so much fuel that flames reach high into the trees above.”

He recommends that leaf litter, bark and branches be cleaned up, and low branches removed where possible.

“When we have really bad fires, the trees haven’t gotten rainfall in six or seven months or more, we can have high Santa Ana winds from the desert, atmospheric humidity is very low, just conditions for really almost any plant to burn,” Ehrlinger explained.

Like all species in the environment, the eucalyptus is affected by changing conditions. It has the advantage of being very tall and resilient, which also means its relative impact on the surrounding environment is large. One thing is clear, it has rooted itself in Southern California and it aims to stay.

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