Coastal fog affects many California plant species and can be critically important to species that experience periodic drought. Drought-deciduous species in particular rely on water availability to maintain their leaves during the summer. To determine fog water use in drought-deciduous plants, this study manipulated access to fog drip and measured the water relations of the common shrub, Artemisia californica, near Santa Barbara, CA. Measuring the stable isotope ratio of hydrogen and oxygen, this study found that A. californica uses fog water in the late summer months when fog is present. This additional water increased plant water content but had no effect on pre-dawn xylem pressure potential. While climatic variability inhibits reliable fog input to A. californica in Santa Barbara, this species can use fog water opportunistically and benefits from large fog events during the summer drought.