The paper investigates the effect of applying different rate of slow disintegrating fertilizer Scotts (Osmocot Exact) with the formula 15:9:9:MgO+Me to the quality of seedlings of marigold and scarlet sage. The marigold and scarlet sage seedlings were grown in poly-propylene containers (speedling system) and poly-propylene pots (pot system). Slow disintegrating fertilizer rate have been applied to the seedlings in the course of their growing (0, 1, 2, 3, i 4 g/l). The obtained data show that the 4g/l substrate rate of slow disintegrating fertilizer has significant effects on the studied parameters of seedlings quality of studied species.