Seed germination characteristics and growing media effects on seedling development of bottle tree (Brachychiton populneus Schott & Endl. R. Br.)

The determination of optimum growing environments and the development of seed propagation strategies are becoming increasingly important in plant breeding, particularly for drought-tolerant species. The bottle tree (B. populneus Schott & Endl. R. Br.), belonging to the subfamily Sterculioideae of the Malvaceae family, is an evergreen ornamental plant characterized by high adaptability and pronounced drought resistance. This study investigated the germination characteristics of bottle tree seeds and the effects of different growing media on seedling development. The research was conducted between 2017 and 2021. The average of thousand-seed weight was 94 g with germination rates ranging from 87% to 99.5% and germination times of 7.6 - 11.2 days. Seed priming with poplar (P. usbekistanica) sawdust extract significantly shortened the germination period in biennial seeds. Growing media significantly affected plant height, stem diameter, and leaf number (p < 0.05). Based on between years differences, the highest increases in plant height, stem diameter, and leaf number were observed in T5-GS+CBC(1:2), T6-GS+CBC(2:1), and T4-GS+CBC(1:1) media, respectively, while the lowest change values were determined in the T2-PS(C) medium. Garden soil and chestnut burr compost promoted seedling growth, whereas poplar sawdust suppressed it. These findings indicate that fresh poplar sawdust can serve as an ecological alternative to chemical growth regulators for plant height control in nurseries. In addition, chestnut compost has been shown to be a sustainable alternative to chemical fertilizers, as it improves soil structure and nutrient availability. The ease of seed propagation and high drought tolerance of the bottle tree highlight its potential as a valuable species for landscaping and climate change adaptation in arid ecosystems.