This study provides a comprehensive and refined framework for the micropropagation of the critically endangered Greek endemic Silene conglomeratica. Using a limited seed stock, a reliable in vitro propagation protocol was developed, supporting both ex situ conservation and potential commercial applications in floriculture and landscape architecture. Nodal explants excised from aseptic seedlings, established on half-strength Murashige and Skoog (MS) medium, were successfully used for culture initiation. Supplementation with 1.0 mg L⁻¹ meta-topolin (mT) and 0.2 mg L⁻¹ 1-naphthaleneacetic acid (NAA) promoted shoot proliferation. Subsequent subculturing on half-strength Rugini Olive Medium (OM/2) supplemented with 0.5 mg L⁻¹ 2-isopentenyladenine (2iP) resulted in high multiplication rates and a high frequency of spontaneous rooting. Rooting initiation was further optimized using OM/2 supplemented with 0.5 mg L⁻¹ indole-3-butyric acid (IBA). The high acclimatization percentage (80%) confirms the feasibility of this protocol for ex situ conservation and highlights its applicability for nursery production and specialized landscape use. Overall, this study contributes an efficient and scalable propagation strategy that supports both the conservation and sustainable utilization of this valuable endemic species. Future work should focus on refining these protocols through more targeted testing of concentrations and alternative combinations of growth regulators and nutrient compositions.

Employing rare or threatened species in ornamental horticulture offers a dual benefit by promoting climate adaptation and enhancing species conservation. Kosteletzkya pentacarpos, an endangered halophytic species, holds potential for introduction into the nursery industry, but efficient propagation methods are lacking. The present study investigated the in vitro propagation of the species using nodal explants excised from aseptic seedlings. A two-stage in vitro culture system was tested with thidiazuron (TDZ) promoting shoot initiation at low concentrations, while higher levels induced callus formation. Transferring micro-shoots to hormone free-, Murashige and Skoog medium (MS) promoted the highest shoot multiplication and elongation. The effect of sodium chloride (NaCl) on in vitro culture was also assessed, with MS media containing up to 5.0 g L⁻¹ NaCl supporting successful culture establishment. Spontaneous rooting was observed during various stages of the culture process. Micro-shoots were rooted at 100.0% on half strength MS medium with or without indole-3-butyric acid, and all plantlets were successfully acclimatized in a peat–perlite substrate (1/1, v/v). Thus, the present protocol provides an efficient system for the large-scale propagation of K. pentacarpos serving as a valuable tool for its conservation and the potential use in the nursery industry.