Density and Species Proportion Effects on Interference between Redstem Filaree (Erodium cicutarium) and Round-Leaved Mallow (Malva pusilla)

Interference between redstem filaree and round-leaved mallow was studied under controlled environmental conditions. Each species was grown in monoculture at densities of 2, 4, 8, and 12 plants per 20-cm-diam pot and in mixtures at all possible combinations of these densities. Leaf area per plant was similar for both species but round-leaved mallow grew taller and produced more shoot biomass than redstem filaree when each was grown in monoculture. Mixed culture responses varied with the proportion density of each species. A reciprocal yield model was tested and modified to account for this significant density interaction. When grown in mixture, round-leaved mallow usually gained in leaf area and shoot biomass at the expense of redstem filaree indicating that it was the superior competitor. Calculated competition ratios indicate that round-leaved mallow was about twice as competitive as redstem filaree under the growing conditions of this study.