The effect of planting date on Kentucky bluegrass (Poa pratensis) sod root growth was examined.  Kentucky bluegrass sod was established in spring, summer, and autumn in 2006 on a sandy loam soil located at the Turfgrass and Landscape Research Facility in Urbana, Illinois.  At 2 week intervals for a total of 10 weeks after establishment (WAE), cores were collected to a depth of 15 cm and analyzed using the WinRhizo System.  The WinRhizo System was used to analyze root architecture including total root length (TRL) and surface area (SA).  Each architectural parameter was categorized into diameter classes, 0 to 0.1, 0.1 to 0.2, 0.2 to 0.3, and >0.3 mm) and depth classes, 0 to 7.5 cm and 7.6 cm to 15 cm.  At the end of architectural analyses, roots were dried and biomasses recorded.  Pre-harvest sod cores were collected and analyzed in order to serve as seasonal controls.  Sod established in spring and autumn followed similar growth patterns and reached pre-harvest levels in terms of TRL and SA within 4 to 5 WAE.  However, root biomass of spring and autumn established sod was up to 50 % less than pre-harvest sod roots.  Pre-harvest sod had a greater proportion of roots within the larger root diameters classes compared to spring and autumn established sod.  Sod established in summer had slower root growth and did not attain TRL or SA of controls within 10 weeks.  Findings show spring and autumn provide optimal environmental conditions to enhance sod root growth compared to summer conditions.  However, measurement of sod root growth using biomass does not accurately indicate important root parameters such as TRL and SA.