Abstract The present work reports the exploitation of starch as a macromolecular matrix in the domain of ‘green’ bio-nanotechnology. The differential templating attributes of starch under ambient aging and sonication for biomimetically generated silver nanoparticles were investigated. Morphology-directing action of the starch-bioreductant (i.e., Mesua ferrea Linn. leaf aqueous extract, adjusted to basic pH) complex resulted in a branched silver structure (∼440 nm, along the long axis with branch average diameter of 11.5 nm) upon aging for 24 days. Starch assisted spherical silver nanoparticles (average diameter, 5.4 nm) were obtained under sonication parameters of 3 min, 0.5 cycles at 60% amplitude, optimized through response surface methodology. Evaluation of phytotoxicity on Cucumis sativus, compromise on amplification of a 263 base pair mammalian DNA sequence in polymerase chain reaction (PCR) and anti-microbial potency demonstrated differential action of the carbohydrate templated aged and sonicated silver nanoparticles at the bio-interface.