Although low water use landscaping is becoming common in arid regions, little is known about drought tolerance and drought responses ofmany ornamental plants, especially herbaceous perennials. Petunia is a common flowering ornamental plant, largely produced for home-consumption and gardening.A factorial experiment based on a completely randomized design with irrigation at 3 levels (100, 70 and 40% FC) and Petunia hybrid (Persian and Petunia hybrida cv. Sonja Pink)in vegetative and reproductive growth stageswas conducted with 4 replicates. Results showed significant differences among measured traits. Obviously a great difference is demonstrated between Persian petunia and Petunia hybrida cv. Sonja Pink in almost all characteristics. Nearly all measured traits are affected by watering regimes. Interactions effects were also outstanding especially in shoot and root dry weights and flower characteristics. Drought stress decreased leaf area, plant height, and roots and shoots fresh and dry weight and root length significantly in both petunias.Highest and lowest values are mainly observed in well water (100% FC) and stress (40% FC) treatments, respectively. Flower number and lateral branches were reduced from 71.87 and 8.5 to 13 and 1, respectively.But main branches and flower diameter were less affected. It generally seems according to the results of this experiment, that petunia is asemi tolerant plant with moderatedrought resistance.

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