Abstract Background Phenotypic traits are indicative of a plant’s resource utilization and survival strategies. Understanding the geographical differentiation of Calamus rhabdocladus phenotypes holds significant theoretical and practical value for genetic breeding and the selection of superior geographical provenances. This study analyzed the geographic variation in 15 phenotypic traits of leaves, stems, roots, flagellums, and other parts from 10 provenances of C. rhabdocladus in China. The phenotypic characters of C. rhabdocladus were measured in the field, while soil factors were collected in the field and analyzed in the laboratory. Climatic data were obtained through online sources. Pearson’s correlation was used to analyze the relationships between the 15 phenotypic traits. Redundancy analysis and variance decomposition analysis were used to quantify the effects of climatic and soil factors on the geographical variation in phenotypic traits of C. rhabdocladus, and the key influencing factors were obtained by comparing the explanatory rates of soil and climatic factors on phenotypic traits of C. rhabdocladus. Results The results showed that the Coefficient of variation (CV) of phenotypic traits among provenances ranges from 7.48 to 182.16%, with root dry weight exhibiting the largest variation. The plasticity indices varied between 0.16 and 0.82, with the flagellum volume showing the highest value. Significant correlations were observed among leaf, stem, flagellum, and root traits. Average air temperature was identified as the crucial climatic factor influencing the phenotypic traits of C. rhabdocladus, while effective nitrogen and organic matter content were the key soil factors influencing these traits. Within the scope of this study, climatic factors provided a better explanation of phenotype variation than soil factors. Conclusions These results highlight the importance of climatic adaptation in shaping phenotypic diversity and suggest that future research should explore the genetic mechanisms underlying these traits and their interactions with environmental factors at finer spatial scales.