Researchers rediscover an oak tree believed to be


image: The search party stands with the only specimen of Quercus tardifolia
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Credit: United States Botanical Garden

LISLE, Ill. (July 7, 2022)—Botanical researchers representing a coalition of more than 10 institutions have discovered an oak tree once thought to be extinct and now in immediate need of conservation in Big Bend National Park in Texas.

Researchers led by The Morton Arboretum and United States Botanic Garden (USBG) were delighted to find a single Quercus tardifolia (Q. tardifolia) tree about 30 feet high, although in poor condition. First described in the 1930s, the last living specimen is believed to have perished in 2011.

“This work is critical to preserving the biodiversity that Earth is losing so rapidly,” said Murphy Westwood, Ph.D., vice president of science and conservation at Morton’s Arboretum. “If we ignore the decline of Q. tardifolia and other rare and endangered trees, we could see countless domino effects with the loss of other living entities in the ecosystems supported by these trees,” she said. According to Westwood, Q. tardifolia is considered one of the rarest oaks in the world, if not the rarest.

Scientists predict that by studying why this tree is disappearing, they may be able to protect other organisms from the same fate. That this specimen of Q. tardifolia can be saved remains in question.

The team that made the discovery on May 25, 2022 described a dire scene. The trunk is fire scarred and shows signs of severe fungal infection. A drought or fire has the potential to end its life, say the scientists who also report that climate change is making that outcome more likely each year. The group is now working with the National Park Service to reduce the immediate threat of wildfire to the tree, and conservationists in this collaboration are moving quickly to return to the search for acorns and attempt to spread, the process of selecting specimens from a mother plant.

“This is important collaborative research necessary for the conservation of Q. tardifoliasaid Carolyn Whiting, a botanist at Big Bend National Park. “The Chisos Mountains are home to a great diversity of oak species, in part due to the wide range of habitats available on this ‘sky island’. There is still much to learn about the oaks of Chisos.

“The United States Botanic Garden is thrilled with the success of this partnership and collecting journey that has rediscovered such a rare oak tree,” said Susan Pell, Ph.D., acting executive director of the United States Botanical Garden, who finances and collaborates in the project. “This discovery is just the beginning of the conservation work we are doing in partnership with The Morton Arboretum to better understand and conserve endangered trees.”

Other collaborators were Bartlett Tree Research Laboratories and Arboretum; Lady Bird Johnson Wildflower Center; NatureServe; Polly Hill Arboretum; San Antonio Botanical Garden; University of California, Davis Arboretum and Public Garden; and the Sul Ross State University A. Michael Powell Herbarium.

What could molecular analysis reveal about Quercus tardifolia?

Oak trees tend to hybridize or crossbreed, which can allow them to adapt more quickly to changing climatic conditions such as extreme heat and new diseases. This frequent hybridization can also blur the genetic lineages between oak species in a given ecosystem like Big Bend. Molecular analysis will confirm whether the DNA of the newly discovered tree matches that of previous samples of Q. tardifolia, but according to the researchers, it is possible that the analysis raises more questions than answers.

According to Andrew Hipp, Ph.D., senior plant systematics researcher and director of the herbarium at Morton’s Arboretum, whose team will perform the genetic analysis, “It’s an interesting problem. We are investigating whether this tree is genetically similar to other trees that have been previously harvested as Q. tardifolia. This should tell us if this collection is the same as the one Cornelius H. Muller named Q. tardifolia. It should also tell us if this collection of specimens is genetically distinct enough from other closely related oaks in the area to warrant recognition as a species.

Regardless of classification, Hipp noted that it is important to preserve more than individual species, but rather all of the genetic variations of life. “Species are genetically distinct populations that we can usually recognize in the field,” he said. “But they are not the be-all and end-all of conservation. We also aim to protect functional variation within species. Leaf shape, physiological responses to drought and fire, and even tree longevity are all attributes that can be shared between populations and between species through gene flow. The functional variation that these new collections represent may be just what is needed to help the region’s oak trees adapt to environmental changes in the near or distant future.

The preservation of oak trees is essential to ecosystems

Oaks are exceptional among tree species in that their acorns cannot traditionally be seed-banked for conservation purposes. According to the researchers, they should be kept in the wild or in living collections, which is why the involvement of botanic gardens is essential. The researchers who discovered the Q. tardifolia tree fear that it will not produce acorns. Other propagation methods, including grafting, are pursued to preserve the future of the oak.

“All over the planet, oak trees serve as ecological anchors by cleaning the air, filtering water, sequestering carbon dioxide, and supporting countless fungi, insects, birds, and mammals,” Westwood explained. “When we’re lost, we don’t know what we might permanently lose in its wake,” she said.

However, Westwood, Pell and others warn that conservation efforts like this require collaborative initiatives, such as the World Oak Conservation Consortiumthe involvement of botanical gardens and various scientific experts to ensure a future for endangered trees.

“In many ways, this tree is an ancient relic. Due to climate change, the world is completely different now than when it evolved,” said Wesley Knapp, chief botanist at NatureServe, who participated in the expedition. “It behooves us to learn from it and protect it while we still can to inform future conservation efforts,” he said. “Nature rarely gives us a second chance, and I doubt we will get a third. We won’t waste it.

Members of the May 2022 expedition that first located the only Q. tardifolia tree included Adam Black of Bartlett Tree Research Laboratories and Arboretum, Michael Eason of San Antonio Botanical Garden, Emily Griswold of UC Davis Arboretum and Public Garden, Wesley Knapp of NatureServe, John Saltiel of USBG, Phillip Schulze of Lady Bird Johnson Wildflower Center, Elizabeth Thomas from Polly Hill Arboretum, Kelsey Wogan from Sul Ross State University A. Michael Powell Herbarium, and Zarah Wyly, an independent oak researcher in California.


About Morton Arboretum

The Morton Arboretum is a world-renowned leader in tree science and research. Its 1,700-acre site includes 222,000 tree and plant specimens, representing 4,650 taxa from 40 countries. The Arboretum’s Center for Tree Science collaborates with researchers around the world, bringing scientific knowledge and technical experience to secure the future of trees. The Arboretum’s Global Tree Conservation Program draws on the expertise of the botanic garden community to protect and restore vulnerable and endangered trees. Additional information about the scientific work of the Arboretum and how it contributes to a greener, healthier world for future generations is available at

About the United States Botanical Garden

The United States Botanical Garden (USBG) is the oldest continuously operating public garden in the United States, established by Congress in 1820. The USBG educates visitors about the importance, fundamental value, and diversity of plants, as well as their aesthetic, cultural and economic aspects. , therapeutic and ecological significance. With over one million visitors a year, USBG strives to demonstrate and promote sustainable practices. It is a living plant museum accredited by the American Alliance of Museums and Botanic Gardens Conservation International.


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