The field experiment was carried out in 2006-2008 in the Felin Experimental Farm (University of Life Sciences in Lublin) on podzolic soil developed from dusty medium loam. Root chicory (Cichorium intybus L.) var. sativum (Bisch.) Janch. cv. Polanowicka was involved in the experiment. The experimental factors were 3 species of intercrop plants: common vetch (Vicia sativa), phacelia (Phacelia tanacetifolia), oat (Avena sativa) and 2 dates of ploughing-in: pre-winter and spring. In total, 26 taxons characteristic for vegetable plantations were identified in chicory weed infestation. Monocarpic species dominated, among which Senecio vulgaris, Chenopodium album, Lamium amplexicaule, Galinsoga ciliata, and Capsella bursa-pastoris were predominant. The date of ploughing-in did not significantly affect the status and size of weed infestation of chicory plots. Short-lived species occurred after pre-winter ploughing-in, while perennial - after spring ploughing-in. The application of intercrops significantly reduced chicory weed infestation as compared to the cultivation with no intercrop. The ploughing-in of Avena sativa biomass appeared to be the most efficient. The intercrop plants reduced the occurrence of Senecio vulgaris and Capsella bursa-pastoris which were the most numerous in the treatment without intercrops. Biomass of Vicia sativa favored the growth of Chenopodium album and Lamium amplexicaule. The secondary weed infestation did not depend on agrotechnical factors applied during the experiment.