This laboratory experiment was conducted in the labs of the Department of Field Crops at the College of Agriculture, University of Tikrit. The study aimed to investigate the allelopathic effect of some aqueous extracts of Eucalyptus (Eucalyptus spp.), Milk thistle (Silybum marianum) and Mallow (Malva sylvestris) on the germination and growth of Basil (Ocimum basilicum L.), Arugula‎‎‎ (Eruca sativa) and common Sow thistle‎‎‎‎ (Sonchus oleraceus) seeds. The experiment was applied using a completely randomized design (independent comparisons). The trial included 12 experimental units and each unit contained 10 seeds for each type of used seeds (Basil‎, Arugula‎‎‎‎‎, and Sow thistle‎‎‎‎‎‎‎). These seeds were treated with the aqueous extracts individually. The extracts used in this experiment were Eucalyptus‎‎‎ plant extract, Milk‎‎‎‎ thistle weed extract, and mallow weed extract, in addition to the control treatment without adding any extract. The studied traits included the germination percentage of the weed seeds, radicle and plumule length also the dry weight of the radicle and plumule for Basil‎ and its associated weeds.
The results showed that the Eucalyptus‎‎‎ extract led to the inhibition of the germination percentage for Sow thistle‎‎‎‎‎‎‎‎‎‎‎ and Arugula‎‎ seeds with means of 46.67 and 53.30%, respectively. Regarding the plumule length we notice that the mallow extract gave the lowest value for Sow thistle‎‎‎‎‎‎‎‎‎‎‎ and Arugula‎‎ plumule length by reaching 2.00 and 2.833 cm, respectively, while the effect of Eucalyptus‎‎‎ extract on the plumule length of Arugula‎‎ reached 2.177 cm.
The results also showed that the mallow extract affected the radicle length of Sow thistle‎‎‎‎‎‎‎‎‎‎‎ and Arugula‎‎ and their means were 0.467 and 1.433 cm respectively. The Eucalyptus‎‎‎ extract had a clear effect on the radicle length feature for Sow thistle‎‎‎‎‎‎‎‎‎‎‎ and Arugula‎‎ where the length for them was 1.220 and 1.267 cm, respectively.
On the other hand, the dry weight of the plumule of Basil‎ plant, the Milk‎‎‎‎ thistle extract treatment recorded its highest mean which was 0.0233 g. Also the Milk‎‎‎‎ thistle extract recorded the highest mean for the dry weight trait of Sow thistle‎‎‎‎‎‎‎‎‎‎‎ and Arugula‎‎  by reaching a mean of 0.02133 and 0.0390 g, respectively.