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Populations of Rumex cyprius were grown from seeds in pots under water treatments equivalent to 50, 100, 150 and 200 mm rainfall. Survival, growth, plant water relations, resource allocation, pigment and tannin content were investigated as a function of time from seedling to senescence. Plants grown under 50 mm did not complete their life cycle and died during the juvenile stage. Increased water availability from 100 to 200 mm resulted in increased survival, relative growth rate, leaf area index, transpiration ratio and succulence. In contrast, root length: shoot height ratio, relative conducting area, pigment and tannin content were lower under the relatively high water availability. The increase in water availability from 100 to 200 mm resulted in more resource allocation to vegetative growth. Under the water treatment of 100 mm, plants went through their life cycle in a shorter time than under the higher watering regimes. Differences in behaviour of Rumex cyprius indicate different degrees of plasticity in response to water availability. The plastic response to different water treatments enables the plants to complete their life cycle, even during years of less than average rainfall.