Allelopathic effect of popular medicinal plants on Fagopyrum esculentum (Moench), Papaver somniferum (L.) and Brassica napus var. oleifera (L.)

Glasshouse experiments were carried out to assess the effect of popular medicinal herbs dry matter on germination and early growth of common buckwheat (Fagpopyrum esculentum), opium poppy (Papaver somniferum) and two cultivars of oilseed rape (Brassica napus var. oleifera). Depending on species of the herb, leaves, inflorescences, fruits and whole plants were used. The greatest stimulatory effect on seedling emergence of common buckwheat was exhibited by Urtica sp. while seedling emergence of opium poppy was most affected by Hypericum sp. Seedling emergence of common buckwheat was reduced by the use of Matricaria sp.  inflorescence, while Euphrasia sp. herb reduced emergence of opium poppy. Urtica sp. leaves caused a significant increase in fresh matter of buckwheat as well as opium poppy. The greatest reduction in fresh matter of buckwheat was noted as a result of using Euphrasia sp.  herb, while in the case of opium poppy, fresh matter was most reduced by using Tilia sp. inflorescence. Mentha sp. exhibited a strong stimulatory effect on seedling emergence of oilseed rape cultivar Californium, while Achillea sp. had an inhibitory influence. All the examined medicinal plants inhibited seedling emergence of semi-dwarf hybrid oilseed rape cv. Maximus. Inhibitory or a stimulatory effect on germination of winter oilseed rape seeds was not always correlated with a reduction or an increase in plant fresh matter.   Key words: Early growth, fresh mass, germination, herbs.