Valeriana glechomifolia, a southern Brazilian endemic species commonly known as Valerian, accumulates the bioactive terpene derivatives valepotriates in all of its organs. In vitro growth of V. glechomifolia on solid Murashige and Skoog (MS) without phytohormones at full, 75% (MS 75), or on a modified formulation (M Δ) was compared in stock cultures kept for up to 9 mo. without subculture. Changes in biomass accumulation, development of roots and shoots, and the production of the valepotriates acevaltrate, didrovaltrate, and valtrate were monthly evaluated. The highest biomass accumulation and root development was observed in plants grown on M Δ, whereas better leaf development was detected in M-Δ- and MS-medium-grown plants after 8 and 9 mo. of culture, respectively. Maximal didrovaltrate and valtrate yields were observed in M-Δ-grown plants harvested after 5 and 6 mo. of culture, respectively, whereas acevaltrate concentration was highest on M-Δ- and MS-75-grown plants after 7 mo. of culture. Plants grown for 6 mo. without subculture in M Δ were successfully propagated, showing stable growth and valepotriate yields three- to sixfold higher that those observed in field-grown plants. The results showed a positive effect of combined moderate reduction in salt concentration and increases in selected micronutrients and myo-inositol amounts on both growth and valepotriate yields of extended period stock cultures of V. glechomifolia.