The experiments carried out in 2006–2007 referred to the growth of marjoram plants, its yields and chemical composition depending on the plant density and harvest time. Four plant densities (setting spacing 20 × 40 cm, 30 × 30 cm, 30 × 40 cm and 40 × 40 cm) as well as two harvest times (beginning of flower bud forming and full blooming) were applied. The lowest density favored the plant tillering, which apparently affected the herb yield. Plants growing at the lowest density (40 × 40 cm spacing) had the largest fresh and air-dried herb yields (0.71 and 0.18 kg m^-2, respectively). Herb of plants grown at denser spacing contained more total nitrogen and nitrates (V) as well as less potassium, than that of plants grown at lower density. The herb harvest at full flowering stage turned out to be favourable because of significantly lover nitrates concentration as compared to other stages. The contents of essential oil was significantly higher in the full flowering stage than in those harvested in the bud formation stage. Plants growing at denser spacing produced more oil. Trans-sabinene hydrate and terpinene-4-ol were dominating components of marjoram essential oil.

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