Herbage and Essential Oil and Yield Composition of Mentha piperita L. in Different Plant Densities in Northern Latitudes

The effect of plant density (10 cm, 20 cm and 30 cm x 50 cm) on the plant growth, herbage yield, essential oil production and composition of Hungarian type peppermint (Mentha piperita L. var. sylvestris Sole) was studied in field experiments in Ruukki, Northern Finland in two two-year experiments. In the first growing season, herbage yields were the highest and leaf/stem ratios the lowest in 10-cm density, but there were no systematic significant differences between different densities. Oil yields per hectare were the highest in 10-cm and 30-cm densities. The oil concentration was highest in the highest plant density but the oil composition was not affected by it.