Abstract. The obtained results showed that the content of the essential oil in thyme and marjoram herb was highly significant different in the investigated years. Analysis of the effect of weather conditions on the essential oil content showed that there was a significant positive correlation between essential oil content in thyme and the mean daily temperature, while for marjoram there was a significant positive correlation between essential oil content and the mean daily temperature and insolation.

The effect of weather conditions on essential oil content
in thyme (Thymus vulgaris L.)
and marjoram (Origanum majorana L.)

Summary

In 1998-2003 the experiment was carried out in the plant-breeding nursery of thyme cultivar ‘Słoneczko’ and marjoram cultivar ‘Miraż’ in Plewiska near Poznań. Each year, 20 samples of herb from individual plants were taken. Essential oil was obtained by hydro-distillation in Deryng’s apparatus following the method of Polish Pharmacopea VI. To evaluate the effect of weather conditions, the average day temperature, total sum of sunshine hours and total sum of rainfall of 31 days before herb harvest were analysed. The obtained results showed that content of essential oil in thyme and marjoram herb was highly significantly different in the investigated years. Analysis of the effect of weather conditions on essential oil content showed that there was a significant positive correlation between essential oil content in thyme and the mean daily temperature, while for marjoram there was a significant positive correlation between essential oil content and the mean daily temperature and insolation.