Weeds are one of the most harmful bioagents, which affect the yield of cultivated plants. Weed flora and vegetation on plantations of medicinal plant crops have been sufficiently investigated neither in our country nor around the world. However, weed control in medicinal plant crops and application of herbicides in particular, is, as it is well known associated with a tendency to provoke environmental and ecotoxicological effects. Considering the fact that medicinal plant production is currently undergoing expansion, there is a rational importance for conducting floristic and phytocoenological research of weed and weed communities in cultivated medicinal plant species. The perennial weeds cause even more serious damage in medicinal plant crops, and therefore the comprehension of their appearance and development, the control and keeping them down, should be treated with special attention.

Qualitative and quantitative analyses of perennial weed plants in several medicinal plant crops were carried out in the fields of the Institute for Medicinal Plant Research "Dr Josif Pančić" in Pančevo near Belgrade. The Braun-Blanquet system and transformed the data on weed abundance and coverage according to a scale by Weshoff and van der Maarel were applied for the purpose of an analysis of perennial weeds determined in medicinal plant crops. Floral elements, life forms, ecological indices are the parameters that were considered, as well.

Our investigation showed that only two perennial weed species, such as Sorghum halepense and Convolvulus arvensis are represented in all medicinal plant crops investigated. The other perennial weeds could be considered as pretty frequent ones, like Cirsium arvense, Sonchus asper, and Capsella bursa pastoris. The total of 40 perennial weeds has been identified in different medicinal plant crops.

The analysis of perennial weeds affecting the growth of medicinal plant species under the controlled conditions, has included the strategies of coping against them, where different forms of perennial weed control, such as agro-technical, chemical and biological were being discussed.

Key words: medicinal plant crops, perennial weeds, weed control.