Hippophae rhamnoides L. (sea buckthorn) is a key multipurpose shrub of Eurasia valued for its ecological resilience, nutritional properties, and economic importance. This study examines the regenerative capacity, cold tolerance, productivity, and vegetative propagation efficiency of H. rhamnoides populations originating from East Kazakhstan and maintained at the Altai Botanical Garden (ABG). Between 1981 and 2024, five natural populations (Kendyrlyk, Kaindysu, Tersayryk, Shetlasty, and Karatal Sands) were evaluated under both natural and introduction conditions. A total of 68 clonal forms were propagated and assessed for longevity, yield stability, and morphological traits. The results demonstrated high ecological plasticity and adaptation to the sharply continental climate of East Kazakhstan, withstanding winter temperatures of -38 to -44 °C without damage. Long-lived genotypes (up to 32 years) exhibited consistent productivity, yielding 3.7–14.5 kg per plant (4.6–17.5 t/ha). Large-fruited cultivars such as ‘Yubileinaya Kotukhova’, ‘Shetlastinka’, and ‘Asem’ reached fruit masses up to 95.8 g of 100 berries. Vegetative propagation by green cuttings proved highly effective, with rooting rates up to 90% when treated with HB-101, exceeding control treatments by 14.7%. Stable thickets formed by root suckers persisted for nearly four decades, confirming strong clonal stability and adaptive capacity. These findings underscore the significant potential of H. rhamnoides germplasm from East Kazakhstan for breeding cold-hardy, high-yielding cultivars suited to continental climates. The research highlights the importance of ex situ conservation at ABG and provides a foundation for further genetic, biochemical, and breeding studies aimed at enhancing the productivity and sustainability of this ecologically and economically valuable species.