A Native American legend holds that the Council Oaks were a location for the launching of war and peace parties. Legends also hold that women of the Tejas tribe would drink a tea made from honey and the acorns of the oaks to ensure the safety of warriors in battle.
As more and more European-Americans settled in Texas, the Council Oaks fell victim to neglect and the development of the city of Austin. By 1927 only one of the original 14 trees remained. The American Forestry Association proclaimed this tree the most perfect specimen of a North American tree, and inducted the Treaty Oak into its Hall of Fame in Washington, D.C.
In 1989, in an act of deliberate vandalism, the tree was poisoned with the powerful hardwood herbicide Velpar. Lab tests showed the quantity of herbicide used would have been sufficient to kill 100 trees. The incident sparked community outrage, national news reports, and a torrent of homemade "Get Well" cards from children that were displayed on the fence around the park. Texas industrialist Ross Perot wrote a blank check to fund efforts to save the tree. DuPont, the herbicide manufacturer, established a $10,000 reward to capture the poisoner. The vandal, Paul Cullen, was apprehended after reportedly bragging about poisoning the tree as a means of casting a spell. Cullen was convicted of felony criminal mischief and sentenced to serve nine years in prison.
The intensive efforts to save the Treaty Oak included applications of sugar to the root zone, replacement of soil around its roots and the installation of a system to mist the tree with spring water. Although arborists expected the tree to die, the Treaty Oak survived. Still, almost two-thirds of the tree died and more than half of its crown had to be pruned.