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Carlos collecting Quercus ×alentejana (Q. faginea × Q. pyrenaica) in northeastern Portugal for his PhD thesis © Carlos Vila-Viçosa
An interview with Portuguese oak conservationist Dr. Carlos...
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Plant Focus

Quercus crassipes acorns with inrolled cupule margin
One of the more well-known Mexican oaks in cultivation.

New Oak Introductions for California

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Dave Muffly

Published May 2023 in International Oaks No. 34: 203–210


California has a long history of planting water-loving trees ill adapted to our arid mediterranean climate. With droughts increasing in duration and intensity since the 1970s, California cities have experienced substantial tree losses, raising the question of what trees are sustainable in these locations. Realizing this need for new trees, a few individuals and organizations began experimenting with new drought-adapted tree species, while other horticulturists noted the unusual survivor trees scattered randomly throughout the state. These trends came to fruition over the last decade, as climate change awareness grew and tree losses continued. At the same time, the massive and radical tree initiative for the Apple Park mega- campus has introduced dozens of new tree types, particularly oaks, increasing awareness in the landscape industry about available alternatives.

Although the landscape industry is rather conservative, this difficult moment in history that is ours requires creativity. Consequently, a few enterprising nurseries are taking risky bets and seeing them pay off. Clients are demanding more choice, more native trees, and more drought tolerance. Oaks, particularly Mexican species, are proving to be popular and excellent performers in a wide range of urban settings. Quercus rugosa, Q. hypoleucoides, and Q. oblongifolia from the American Southwest and Mexico are leading new species. The rare California native oak Q. tomentella is being planted intensively, and soon there will be more urban-planted Q. tomentella than wild trees. Learning the details of tree testing and introductions in California may prove useful to others facing similar transitions throughout the world.