The main objective of the present study was to investigate the phytotoxic effects of five medicinal plants;
Colocynthis vulgaris Schrad, Retama retam L, Traganum nudatum Del, Pituranthos chloranthus Benth. &
Hook.and Artemisia herba-alba Asso on germination efficiency, germination index and radicle length of the
two dominant weeds; Avena fatua L. and Polygonum convolvulus L. in Algeria. The results showed that the
aqueous root extract of the five donor species has no allelopathic effect on the measured parameters of the two
weed species. On the other hand, the shoots exhibited a significant effect only on Avena fatua, while
Polygonum convolvulus was highly suppressed by shoots of Colocynthis vulgaris and Traganum nadatum.