This experiment measured plant growth of a halophyte (species adapted to saline conditions) confetti tree (Maytenus senegalensis) using runoff from kneeholy plants (Ruscus aculeatus). Three irrigation treatments were used, a standard nutrient solution or control (T₀), runoff water collected from kneeholy plants irrigated with the standard nutrient solution blended 50:50 with tap water (T₁), and 100% runoff water collected from kneeholy plants irrigated with the standard nutrient solution (T₂), in which the nutrient concentrations were analyzed by high-performance liquid chromatography. Growth, photosynthetic parameters, and mineral composition were measured at the end of the experiment. Electrical conductivity and pH increased with increasing runoff application (decreased blending). Treatment 2 had significantly higher plant height, number of branches, number of leaves, leaf area index, and dry weight. Treatments 1 and 2 had significantly lower root lengths compared with the control. Chlorophyll concentration and green index color in leaves were greater in T₂ and T₁ than T₀. The mineral composition of roots and leaves was affected by irrigation treatment, resulting in an increase of sodium and chloride concentration and a decline of nitrogen and phosphorous concentration compared with the control. The reuse of runoff water was beneficial for growing this commercially important halophytic species in Spain, a consideration that is particularly relevant in locations with water quality, quantity issues, or both.