In clonal plants, plasticity in spacer length and branching allows for placement of ramets in favorable microenvironments. We investigated shoot density, rhizome biomass, and leaf scars in populations of Acorus calamus L., an emergent macrophyte, in southeast Ohio. To evaluate the influence of edaphic factors on rhizome plasticity, soil, shoot density and rhizomes were sampled from A. calamus populations. MANOVA indicated no overall significant difference (λ = 0.29, P = 0.22) in most soil variables within a patch. However, there were significant differences among population patches in soil variables (λ = 0.00006, P < 0.001), shoot density and morphometric variables (λ = 0.45, P < 0.001). Correlation analysis suggests that rhizome length is correlated with soil calcium (r = 0.75, P < 0.01), aluminum (r = −0.55, P < 0.05) and magnesium (r = 0.55, P < 0.05). Redundancy analysis (RDA) indicates that rhizome length, biomass and total number of leaf scars are positively related to a soil calcium gradient. Shoot density increases along a silt and nitrogen gradient but decreases with organic matter content. Our study suggests that Acorus calamus is a stress tolerator that displays plasticity in rhizome length and shoot density with respect to nutrient availability.