ABSTRACTRumex alpinus L. (R. alpinus) is a non‐native invasive plant in Czech mountain regions, altering ecosystem structure and function in protected areas. Rumex obtusifolius L. (R. obtusifolius) is a native species and a problematic weed in Czech meadows, while Rumex longifolius DC. (R. longifolius) is characteristic of Fennoscandia and widespread in northern and central Europe. This study explores temperature‐driven germination patterns in R. alpinus, R. obtusifolius, and R. longifolius and also focuses on potential differences across populations of R. alpinus. The hypothesis suggests that R. alpinus is not established in lowland areas due to temperature limitations during germination. A second experiment evaluates the influence of native and non‐native localities on R. alpinus seed germination. The primary experiment was conducted at 6°C, 12°C, 18°C, 24°C, 29°C, and 35°C in a climate chamber, while the second experiment was performed at 24°C for 14 days. Contrary to expectations, R. alpinus exhibited the highest germination rate across all temperatures. In the second experiment, germination rates varied significantly, with a positive correlation between germination success and transition from Alpine to Czech localities. The highest and fastest germination was observed in seeds from the Krkonoše Mountains, where R. alpinus is an invasive plant species.