Bahiagrass, Paspalum notatum Flügge, is a stoloniferous grass that is extensively grown in southeastern USA. Bahiagrass germplasm differs markedly in seasonal forage production. This might be partially related to genotypic variability for developing deep roots. Deeper roots can recover additional soil water and nutrients, particularly nitrogen. The objective of this research was to observe genotypic differences in root depth development rates (RDDR). The effect defoliation had on RDDR was also determined. Plants from the cultivar Argentine and the experimental hybrid Tifton-7 were grown in 1-m long, covered, clear acrylic columns (3.5-cm or 10-cm diameter), containing a sandy soil or potting mix. Two trials in 2006 (16 May to 17 July, and 7 August to 7 October) were located outdoors in Gainesville, FL. The depth of the deepest visible root was recorded three times per week. Above- and below-ground plant mass were determined at the end of each trial. Plants in the second trial were defoliated every one or two weeks, beginning on 9 September. There was no RDDR difference between soil media but greater rates were recorded from the larger columns. Even so, the growth pattern was similar between the two column sizes. Greater RDDR was observed for Tifton-7 (2.6 cm d-1) as compared with Argentine (2.2 cm d-1) between 16 May and 12 June. Tifton-7 also produced greater above- and below-ground mass during the first trial as well as greater above-ground mass during the second trial. Greater RDDR were observed during the first trial, which may be related to greater daily solar radiation during this period. Defoliation treatments (one or two week intervals) slowed RDDR and decreased above and below ground plant mass similarly and independent of genotype. Field studies will be used to verify column results.