Hairy root cultures of Salvia tomentosa were initiated by transformation with Agrobacterium rhizogenes. To prevent necrosis in the explants and to protect young hairy roots, Amberlite XAD-4 resin, in combination with a temporary immersion cultivation system, was applied. HPLC analyzes showed that the resin adsorbed more than 93% of the released phenolic acids and 100% of the released flavonoids. The decreased content of the released phenolics significantly reduced their destructive effects on the plant tissues, prevented, and speeded up the appearance of hairy roots.