Five size ranges of sand and gravel aggregate, as well as mixtures of various proportions of the aggregate size ranges, were used as media to grow Penncross bentgrass (Agrostis palustris Hud.). Rate of root elongation and root dry weight were noticeably reduced when the finest grade aggregate ( < 0.5 mm) was used alone. The intermediate size ranges of 0.5 -1.0 mm appeared best suited to root growth. However, in the mixtures, where the finest size range was limited to a maximum of 20% by volume, there was no significant difference in root mass. The high percolation rates in the 2 coarsest aggregates (1.5 -3.00 mm and 1.0 -1.5 mm), and the lower percolation rate and particularly the amount of pore space filled with water in the finest grade, made this aggregate unsatisfactory for root growth. Capillary uptake and the amount of water in the pore space rose, and the percolation rates fell, as the amount of the finest aggregate in the mixture increased. Layers of the finest material in the profile severely reduced percolation and root penetration.