Bryan Ave eucalyptus tree windrow (Irvine, California)

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In Irvine, there are currently about 12,500 eucalyptus trees on private property (either The Irvine Company land or HOA property) and about 5,700 trees on public property. These are arranged in 38 windrows, stretching predominantly in northwest-southeast direction, parallel to Santa Ana Mountains. The trees were originally intended as windbreakers to protect the citrus groves from the Santa Ana winds blowing from the mountains. As of today, the windrows have no agricultural use since the citrus growing industry that gave name to Orange county has left Irvine.

The oldest of Irvine's windrow eucalyptus trees were planted by George Irvine in the late 1800s. Another round of planting occurred between 1920 and 1940, again for agricultural purposes. As of 2009, the trees are roughly between 70 and 100 years old. The lifespan of Eucalyptus globulus, which are native to Australia and had to be imported, ranges from 50 to 150 years, dependent on growing conditions, soils, and overall care.

Irvine windrow trees were generally neglected for their first 30 to 60 years. As agricultural windbreaks, they received minimal care. When orchards were replaced with row crops, the eucalyptus trees were seen as blocking sunlight and reducing harvest. They were, as a result, routinely damaged from improper pruning practices. The trees were not provided supplemental irrigation, but opportunistically took advantage of crop irrigation. As agricultural fields were converted to urban development, the trees again were often damaged or encroached upon during grading and construction. Following development, the trees have been provided a much higher level of care and maintenance.

The City ordinance prohibits removal of any eucalyptus trees that are part of the windrows, whether on public or private property, without an explicit permission from the City.

As the trees on the public land decay from age, insect damage or external factors, they are cut down by the City of Irvine. While the City landscapers aim to fill the gaps in the windrows with new trees, they will not plant a new eucalyptus tree if another eucalyptus tree is within 20 ft.

The trees are trimmed on a two-year schedule by a contracting firm. A comprehensive study was completed in 2007 with the assistance of staff from UC Riverside and Cal State Fullerton aiming at providing a method for evaluating the health of any given tree, as expressed by the estimated level of internal decay. As a result of the study, the City has come up with plans for future maintenance of the trees, both on public and HOA lands.

Here is how The Irvine Company highlights the aesthetic and historic aspects of the eucalyptus windrows in their marketing materials:

"The land upon which the village of Northpark emerged features eucalyptus trees planted in linear rows by The Irvine Company decades ago as sentinels against Santa Ana winds that roared down from the mountains onto the former agricultural land.

By the time planning for Northpark began in earnest in the 1990s, the eucalyptus trees were full grown, creating towering green rows visible for miles. Major design aspects of the village - from the layout of streets to the locations of homes, parks, schools and shopping centers- were planned around the windrows, preserving an important chapter of the land's history while imprinting an immediate identity on Northpark." (Source: www.goodplanning.org/themasterplan/landscape.asp)