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Forest plantations, including those of Norway spruce, are increasingly threatened by drought in Central Europe. One of the measures understating this threat might be the use of drought-mitigative additives at planting. The effects of induced water limitation and the application of hydrogel Agrisorb and commercial ectomycorrhizal fungi (EMF) inoculum Ectovit on the development of 2 + 1 spruce seedlings were estimated in this study. The root systems of 2 + 0 seedlings were treated with the additives, along with their spring transplantation into peat-filled pots. The seedlings were then exposed throughout the entire growing season either to full watering (FW)—volumetric soil water content 70%, reduced watering (RW)—water content 40%, periodic watering (PW)—substrate rehydrated to 70% after drying to the wilting point (21%), or remained non-watered (NW). Survival, growth and chlorophyll fluorescence of the seedlings decreased proportionally to the increased drought intensity, while the highest root-to-shoot ratio and EMF colonization of roots occurred under PW and RW, respectively. NW seedlings died after 9 weeks of desiccation, whereas the EMF inoculum prolonged the survival time by one week. Ectomycorrhizas were formed predominantly with native EMF in all the treatments; nevertheless, compared with the uninoculated control, the formation of a treatment-specific EMF root morphotype and increased EMF colonization under PW and RW were observed on the inoculated seedlings. Both the EMF inoculum and the hydrogel increased survival under PW by approximately 15% but did not significantly affect growth, regardless of the watering regime. These results are limited to the experimental conditions and suggest a more dominant effects of the watering regimes compared with the additives tested.