The carbon dioxide (CO2) concentration of Earth's atmosphere continues to rise. Plants in general are responsive to changing CO2 concentrations, which suggests changes in agricultural productivity in the United States and around the world. The ability of plants to absorb CO2 during photosynthesis and then store carbon in their structure or sequester it in the soil has potential for mitigating the rate of rise of atmospheric CO2 concentration. Since 1987, Bruce Kimball and coworkers at the USDA Agricultural Research Service in Phoenix, Arizona, have maintained a greenhouse gas experiment using sour orange trees maintained in a CO2- enriched environment. These trees were harvested in 2005. During the final massive harvest, many different properties and characteristics of the woody biomass for these sour orange trees were studied. This report focuses only on the mechanical property evaluation of modulus of elasticity (MOE), specific gravity, and microfibril angle. In this study of CO2-exposed sour orange trees, CO2 did not significantly affect specific gravity of sour orange trees. Exposure to CO2 did not significantly affect MOE of sour orange trees. Exposure to CO2 did, however, seem to influence microfibril angle development. Minor interactions between CO2 and cardinal direction affected the MOE and were caused by experimental difference in chamber construction.