A study was conducted on two high value threatened medicinal and aromatic herbs of Himalayan region, viz., Angelica glauca Edgew. and Heracleum candicans Wall. to determine the optimal age of seedlings for field transplantation along an altitudinal gradient. Thirty, 60, 90, and 120 days old seedlings were transplanted at Shat and Silha sites in Parbati Valley, Kullu district, Himachal Pradesh, India (1800 and 2200 m altitude respectively). Results showed that 90 and 120 days old seedlings of both species had significantly (p < 0.005) higher survival compared to younger seedlings. Furthermore, survival in both the species was significantly (p< 0.05) higher at Silha (high altitude) and mortality especially for A. glauca was very high at Shat (low altitude), implying a narrow range of adaptability for this species. Transplanting 90 to 120 days old seedlings above 2200 m altitude is recommended to achieve optimum survival rates.