The effect of covering and harvesting time on biomass production and essential oil production of Melissa officinalis was evaluated. The experiment was carried out at the Estação Experimental de Canguiri, Pinhais, Paraná State, Brazil, from November 2005 to May 2006. The treatments included pine needles, black plastic and control without covering. The experimental design was of randomized blocks in split plot in time with six replications and 20 plants per experimental unit. Three harvests were performed (84, 134 and 191 days after planting), cutting the stems at 10 cm from the soil surface. The fresh and dry masses per plant and essential oil yield by hidrodestilation were determined. There was no significant effect of the interaction between the mulch and the harvesting time for the evaluated characteristics. A decrease in biomass production was observed at the third harvest, where the average of dry mass production was of 976 and 1135 kg ha-1 at the first and second harvest respectively, reducing to 781 kg ha-1 at the third harvest. The essential oil production also decreased with the successive harvests, being 4.63; 2.97 and 0.43 L ha-1 at the first, second and third harvest, respectively. The type of mulching did not interfere in biomass and essential oil production of M. officinalis. The vegetative growth and essential oil accumulation of M. officinalis decreased in the autumn harvest in Pinhais.
Melissa officinalis; medicinal plant; essencial oil; mulch
