Experimental wetlands were built to follow the implementation and permanence of three species of aquatic macrophytes (Scirpus californicus, Typha subulata and Zizaniopsis bonariensis) under different treatments (water, water + nutrients and water+ nutrients + refinery effluent). Morphological variables (number of lateral shoots produced, height of the main lateral shoot and final density values) were used to check the influence of a petrochemical effluent. All the response variables showed significant differences (p = 5%) in their development, mainly between the water treatment and water + nutrient + effluent, followed by water with water + nutrients. In the Water treatment, the lowest variable values were found for the three species, possibly due to the lack of nutrients in the medium. Opposite results were found in the other treatments, indicating that the petrochemical effluent was not a limiting factor for the implementation of the species in the systems.