Argemone mexicana is known to have significant effects on cultivated agricultural fields. However, there is little information about allelopathic effect of A. mexicana on the growth of wild plant species such as those found in wildlife protected areas. This review presents evidence that allelochemicals present in A. mexicana may affect the overall growth of other plant species.

The present study was conducted in the laboratory to investigate the allelopathic effect of Mexican poppy (Argemone mexicana L.) to the germination and growth parameters of two native species Brachiaria dictyoneura L and Clitoria ternatea L. Different concentrations of leaf and seed aqueous extracts from Argemone mexicana (0%, 25%, 50%, 75% and 100%) were evaluated. Results showed that seed germination, root length, shoot length, seedling length, fresh weight and dry weight of B. dictyoneura and C. ternatea seedlings were significantly reduced by leaf and seed extracts compared with control treatments. Roots were more affected than shoots; and leaf extract was more suppressive than seed extracts. From the results, it is concluded that leaf and seed extracts have some allelochemicals with inhibitory effect on germination and growth of the tested plant species.