The effect of environmental changes in summer on the leaf health of Quercus myrsinifolia planted in pots and in the ground was evaluated by measuring chlorophyll fluorescence parameters. An increase in the consecutive dry days (CDD) and temperature affect the chlorophyll fluorescence parameters. However, the observed effects differed between Q. myrsinifolia planted in pots (dry : PD, watered : PW) and in the ground (dry : GD, watered : GW). The maximum quantum yield of photosystem II (Fv/Fm), the quantum yield of photochemical reaction under light (ΦII), and non-photochemical quenching (NPQ) were lower in PD than in PW and GW throughout the measurement period. Fv/Fm, ΦII, and NPQ tended to decrease with the increase in the CDD due to severe photoinhibition of PD. Additionally, the effect of temperature was compared between PW and GW. When the temperature increased, NPQ was increased in PW. This, in turn, resulted in a large decrease of ΦII at high temperatures, whereas GW did not show such a tendency. These results suggest that potted plants are more sensitive to drought and high-temperature stress than ground plants.