Bombax malabaricum DC. is a deciduous tree that can grow in the dry-hot valley biome of southwestern China. In the dry-hot valley, the adult trees of B. malabaricum produce many seeds, however, few seedlings are found around the mature trees. This discrepancy has important consequences for conservation and reforestation efforts. Therefore, we measured the physical and biological characteristics of seed germination to determine the required environmental factors for natural seed germination. The average weight of 1000 seeds was 39.08 g; the percentage of viable seeds tested via 2,3,5-triphenyl tetrazolium chloride (TTC, 1.0%) was 64.0%, similar to the percentage of germination under controlled conditions (25 to 35 ℃). The seeds of B. malabaricum had good water-absorption capacity; they began to germinate after soaking in distilled water for 2 days at 25 ℃. Seed germination was not sensitive to light and seeds germinated at a broad range of temperatures (15 to 35 ℃). Temperatures ranging from 25 ℃ to 35 ℃ had no significant effect on seed germination percentage. However, germination rate and seedling growth increased with temperature. Germination was sensitive to osmotic stress and decreased significantly in 0.10 g/mL Polyethylene glycol (PEG) solution, compared to the control in distilled water, and no germination occurred at 0.15 g/mL PEG. Seeds soaked in distilled water for 24 h at room temperature were sensitive to heat shock and germination percentage decreased significantly after heat shock for 2 h at 42 ℃. Pre-treatment by soaking with salicylic acid (SA, 1, 10, 100 mg/L) for 24 h with room temperature did not improve drought and heat tolerance of seeds during germination. In conclusion, drought and heat are two key factors that limit seed germination of B. malabaricum. However, an excess of water could also lead to seedling death after germination at relatively high temperatures.