SOIL physical properties of a growing medium are important ……. for optimal plant growth. The present factorial pot experiment was carried out at the Faculty of Agriculture, Cairo University, Giza, Egypt, during two successive seasons of 2010 and 2011. The study aimed at investigating the effects of synthetic commercial amendment (hydrogel) levels applied under two irrigation rates, to assess their influence on some sandy soil physical properties and buttonwood (Conocarpus erectus L.) seedlings growth traits. The irrigation rates were 65 and 35% of the available soil moisture depletion (ASMD), whereas the hydrogel levels were 0.00 (control), 0.05, 0.10 and 0.20%. Soil physical properties were evaluated by determining the total porosity, field capacity, wilting point, available water, and soil bulk density. Moreover, the plant height, root length, shoots and roots fresh and dry weights and shoots: roots ratio, as expressions of seedlings growth responses, were also measured. Generally, the sandy soil physical properties, as well as the seedlings shoot and root growths, were improved by increasing hydrogel concentration in the soil when compared to their controls. The two irrigation rates also affected both of the soil properties and the seedlings growth. Furthermore, the highest concentration of the hydrogel amendment under 35% ASMD prolonged the soil water loss time; increased the field capacity, which reflected on the soil available water; encouraged the formation of aggregates that, in turn, decreased the soil bulk densities; and hence improved the seedling shoots and roots growth biometrics. This study demonstrates also that the addition of hydrogel to planting medium under different irrigation rates increases water use efficiency by preventing applied moisture from infiltrating beyond plant root zones and maximizing the portion of applied water available for plant uptake. Thereby amended sandy soil with hydrophilic-gel can be used in arid and semi-arid areas to provide a better environment for seedlings to grow.