The annual water status and phenological patterns of Rosmarinus officinalis plants in relation to irrigation were studied to improve the use of this species in gardening conditions. Rosmarinus officinalis seedlings were pot-grown for 4 months in the nursery. After this period, plants were transplanted to field conditions before three irrigation treatments were applied from Nov. 2000 to Dec. 2001 (control and deficit treatments: C, T-1 and T-2, respectively). The total amount of water applied by irrigation during the experimental period was 167 mm for control, 83.5 mm for T1 (50% of the control), and 50 mm for T-2 (30% to the control). Two main periods of vegetative growth (beginning of spring and fall) were observed in all treatments. At the end of the experimental period, deficit irrigation had altered the morphology of the R. officinalis plants, reducing plant height and shoot growth. Maximum flowering intensity occurred at the beginning of fall for all irrigation treatments. Deficit irrigation treatments induced a more intense flowering density, although of lower longevity than control plants. The annual pattern of shoot water potential at predawn reflected the irrigation regimes, although less difference resulting from irrigation effect was detected in this parameter at midday. Plants under deficit irrigation showed a conservative strategy in the use of water, reducing stomatal conductance. This finding may be of use for the successful gardening of Rosmarinus officinalis plants in semiarid conditions.