Potted Osteospermum hybrida plants grown in a greenhouse during the Winter were irrigated with water having electrical conductivities (EC) of 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 or 5.0 dS m⁻¹. The following relationships were studied in order to improve the management of saline irrigation systems using soil moisture and EC sensors: pore water EC (EC_PW) using the pour-through method (EC_PWPT) vs. EC_PW estimated using a GS3 sensor (EC_PWGS3); EC_PWPT vs. bulk EC (EC_B); EC_PWPT vs. leachate EC (EC_L); and EC_PWGS3 vs. EC_B. The tolerance of Osteospermum plants to salinity was also determined. Bulk EC, EC_PWGS3, and EC_L values were closely and positively correlated with EC_PWPT. EC_L over-estimated EC_PWPT, while EC_PWGS3 underestimated EC_PWPT. Estimation of EC_PWGS3 (by the Hilhorst Model) was not accurate due to the influences of humidity, salinity, and temperature. The higher the irrigation water EC (EC_IW), the greater the variability in all measurements made of EC. Increases in EC_IW reduced plant height, diminished the aerial dry biomass, and encouraged the presence of basal leaves with necrotic damage. These results highlight the moderate salinity tolerance of Osteospermum, which was related to the efficient accumulation of Cl⁻ and Na⁺ ions in its leaves.