Use of Jiggs bermudagrass [Cynodon dactylon (L.) Pers.] for hay has increased in warm climates like southern Florida, but effects of defoliation and K fertilizer management on Jiggs adaptation to environments with frequent winter freezes are not known. During 2 yr, K fertilization (0, 17, and 34 kg K ha⁻¹ harvest⁻¹) and cutting stubble height (SH, 8 and 16 cm every 28 d) effects on herbage accumulation (HA), ground cover, K removal, and tissue and soil K were evaluated for Jiggs and ‘Tifton 85’ (Cynodon spp.) bermudagrasses. All treatments received 240 kg N ha⁻¹ yr⁻¹. Herbage accumulation was greater for 8- than 16-cm SH (8050 and 7330 kg ha⁻¹ yr⁻¹, respectively) and increased linearly from 7040 to 8120 kg ha⁻¹ yr⁻¹ with increasing K fertilization. Potassium fertilization did not affect grass percentage ground cover, but Jiggs had 17 (2014) and 40% (2015) greater cover than Tifton 85. Increasing K fertilization increased tissue K concentration (15 to 19 g kg⁻¹ in 2014 and 13 to 25 g kg⁻¹ in 2015) and K removal in HA (from 104 to 149 kg ha⁻¹ in 2014 and 88 to 216 kg ha⁻¹ in 2015). During 2 yr, soil-extractable K declined 6 mg kg⁻¹ for the zero K level but increased 6 mg kg⁻¹ when K was applied. In a cooler subtropical region characterized by frequent winter freezes and across a range of K fertilizer and SH levels, Jiggs sustained ground cover better than Tifton 85, but K fertilization did not affect persistence.