A simple control method for virtual plant morphology was presented. The topology structure of plant was obtained from L-system. In L-system, the value of plant parameters was controlled by regular curve, cubic spline curve and B-spline curve. The plant morphology was varied by the modified parameters curve shape, the hypotaxis was determined by using correlation model with both plant parameters and curves. The results showed that the length parameters, angle, and color could be represented by B-spline curve, cubic spline curve and regular curve respectively, and the plant morphology was similar with curve shapes. The method is helpful in future plant modeling.