The scarcity of fresh water and the need to improve environmental management has led to saline water being used for agricultural purposes, and this, in turn, has to be managed in such a way that it minimizes any damage it may cause. The use of soil moisture and electrical conductivity (EC) sensors can play an important role in this process. This work studies whether, by setting different levels of pore water EC (ECPW) in a programmable automatic irrigation system connected to GS3-Decagon sensors, it is possible to create different saline conditions for cultivating geranium in pots irrigated with reclaimed wastewater of 5.5 dS m−1 and fresh water of 1.6 dS m−1 (for flushing). Five treatments were studied: the control (using fresh water) and four saline treatments programmed to provide flushing with fresh water every time that a threshold of ECPW was exceeded: 5 (T5), 5.5 (T5.5), 6 (T6) and 6.5 (T6.5) dS m−1. The saline conditions that the plants could support were evaluated in terms of growth, chlorophyll content, photosynthesis, stomatal conductance, leaf saline ion concentrations, water consumption and drainage. At the end of the experiment, the plants of T5 showed a good ornamental appearance although they had consumed 32% less total applied water than the control. The plants of the other saline treatments were excessively small and showed poor development. The automatic irrigation system using the GS3 was capable of maintaining different conditions of salinity up to 5.5 dS m−1 of ECPW.