The establishment of high-quality turf on soils with limited water-retention capacity requires amendments that improve both nutrient availability and root-zone conditions. This study evaluated the effects of exogenous organic matter and water-retaining soil amendments on the growth dynamics, root morphology, physiological condition, and visual quality of perennial ryegrass (Lolium perenne L.). A three-year field experiment was conducted in eastern Poland from 2018 to 2020 using a split-plot design. The first experimental factor included sewage sludge-derived compost, sewage sludge granules, and an untreated control, while the second comprised coconut fiber, hydrogel, their combination, and a control without water-retaining amendments. Seedling emergence, shoot number, growth intensity, root length and dry mass, leaf chlorophyll index (SPAD), and turf visual quality were assessed. Compost increased seedling emergence and shoot number by 19.6% and 27.7%, respectively, compared with the control. The combined application of coconut fiber and hydrogel increased these parameters by 35.4% and 42.1%, respectively. Both forms of exogenous organic matter significantly enhanced root development. Mean root length increased from 13.5 cm in the control to 18.0 cm with compost and 19.2 cm with granules, while root dry mass increased from 4.1 to 5.5 and 5.1 g, respectively. Water-retaining amendments also improved root morphology, with the combined coconut fiber and hydrogel treatment producing the longest roots and the greatest root dry mass. The amendments increased SPAD values and improved turf visual quality, particularly when sewage sludge granules were combined with coconut fiber and hydrogel. The results demonstrate that integrating exogenous organic matter with water-retaining amendments can improve perennial ryegrass establishment, root development, physiological condition, and turf quality under variable hydrothermal conditions.