Competitiveness of the Exotic Silphium perfoliatum against the Native Urtica dioica: A Field Experiment

Figure 2

Treatments of S. perfoliatum and U. dioica. Both species were planted as control without competition (a, d), surrounded by eight plants of S. perfoliatum (b, e) and surrounded by eight plants of U. dioica (c, f). Distances between surrounding plants and to the respective central plant were 0.4 m. Distances of control plants to plot edges were 0.6 m. n = 9 per treatment.