The growth response and photosynthetic activity of Taxodium distichum in relation to the leaf and root Na content was assessed with the use of 2-year-old seedlings submerged in saline. Seedlings were submerged in water containing 0, 4000, and 8000 ppm NaCl during May, July, and September, respectively. Submergence and soil flooding with fresh water (control) did not inhibit vertical or lateral seedling growth. No morphological changes were observed during submergence in salt water; however, in July and September, leaf injury and shoot dieback were observed in the drained seedlings. Saline submergence in July and September inhibited photosynthesis and decreased the leaf and stem biomass but did not affect the root biomass. The seedling Na and K ion contents increased with increases in salt concentration; however, in May, the ion contents did not increase significantly. Such seasonal differences in ion content might lead to variations in the extent of leaf damage and growth inhibition after saline submergence in T. distichum seedlings.