There was perhaps no one better than Cornelius H. Muller—one of twentieth-century America’s most notable oak fanatics—to document the continent’s most mysterious oak trees. In July 1932, the horseback-riding botanist first encountered Quercus tardifolia while collecting samples in the steep-cut canyons of Texas’s Big Bend National Park. Muller jotted down details of the twigs (slender, somewhat fluted), buds (hairy at the tip), leaves (dull blue-green), and branches (short, stiff). He anointed it with a Latin name that referenced the tree’s late-season leaf development. This process of scientific description is a kind of sacrament, a communion between scientist and species: Muller saw Q. tardifolia, and so it was.
Then, as suddenly as it blinked into taxonomic existence, the species vanished from sight.
In Muller’s wake, a succession of ecologists have scoured Big Bend for more of the species, trying to prove that it exists. None have succeeded. Ecologists only ever found one possible Q. tardifolia tree—which may or may not have been Muller’s original specimen; it died around 2011, before it could be genetically analyzed or botanically cultivated for conservation. Today, Q. tardifolia has grown about as lonely as a species can get, with an estimated population in the double digits and a known range of one location.