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Residue incorporation greatly modifies the soil chemical properties, and regulates seed germination and subsequent growth of neighboring species by inducing metabolic changes. Such growth regulatory effects often vary among cultivars and the stage of growth of donor plants. Little information is available on the induced biochemical changes in receiver plants and the soil chemical properties when wheat residue collected at different growth stages is incorporated into the soil. Bioassays were conducted to appraise the allelopathic potential of residue (8 g kg soil) of hexaploid wheat (Triticum aestivum L.) cultivars (Millat-2011, AARI-2011, Lasani-2008 and Faisalabad-2008) collected at tillering (Z-30), anthesis (Z-60) and maturity (Z90)] against canary grass (Phalaris minor Retz.). Mean emergence time of canary grass was prolonged over control by soil incorporation of residue at anthesis and maturity stages of cultivars AARI-2011 and Lasani-2008. Final emergence percentage declined by 13‒31% for residue collected at different growth stages. Maximum suppression in shoot (33‒51% and 28‒53%) and root (34‒52% and 28‒54%) length and seedling dry biomass (66‒88% and 58‒86%) of canary grass over control was also recorded under aforementioned treatment combinations. Total chlorophyll contents in canary grass declined in response to soil incorporation of residue at anthesis and maturity stages of all wheat cultivars but an increase was recorded for residue incorporated at tillering stage. Phenolic contents in residue and residue-amended soil increased with advancement in stage of wheat growth. Biochemical bases of phytotoxicity and changes in activities of enzymatic antioxidants in canary grass seedling are discussed. Such information suggests the growth regulatory potential of residue of specific wheat cultivars against weeds of economic significance in wheat based cropping systems and scope for increasing nutrient status of soils. © 2016 Friends Science Publishers