Intensive mowing has contributed to the loss of some climax grasses in Texas highway rights-of-way. The overall objective of this study was to evaluate the effect of different mowing heights and frequencies on total non-structural carbohydrate (TNC) concentration and tiller density in short and mid-grasses grown along highway rights-of-way. Shortgrasses were represented by blue grama [Bouteloua gracilis (H.B.K) Lag ex Steud.], and mid-grasses were represented by silver bluestem [Bothriochloa saccharoides (Sw.) Rydb], both of which are indigenous species. During 1999 and 2000, grasses were either non-mowed (control) or subjected to mowing heights of 5 and 10 cm, and 5 mowing frequencies (monthly, bi-monthly, tri-monthly, 1-time-only at the beginning or end of the growing season). Plants of both species mowed less frequently at either stubble height had higher TNC concentrations than plants subjected to more frequent mowing. Mowing produced fewer (P < 0.05) tillers after 2 consecutive mowing seasons than after 1 mowing season in silver bluestem. Silver bluestem tiller growth was more susceptible to frequent mowing than blue grama. Mowing during periods of rapid inflorescence development reduced tiller density in both species after 2 mowing seasons. Mowing height and frequency guidelines are proposed to maintain roadside grasses in their most productive state through planning mowing practices around the target plant's natural growth habit and it's ability to respond to defoliation.