Present work reports the synthesis of ZnO flowerets consisting of nanorod petals of ZnO having a mean aspect ratio ∼9, supported on micron sized Ni-enriched particles of size in the range of ∼1–4 μm and also free-standing pure ZnO nanorods from mechanically alloyed Ni-Zn powder particles via selective leaching in NaOH solution. Optimization of the composition of the initial alloy powder, the concentration of NaOH and time of exposure in the solution was carried out to get to the ZnO flowerets with an increment in the surface area of the order of 400%. The mechanism and reaction chemistry of ZnO nanorods formation and growth were explained based on the evidence of various characterization techniques including inductive coupled plasma mass spectroscopy (ICP-MS) and electrochemical measurements. Free-standing pure ZnO nanorods were also synthesized by ultrasonically breaking the rod petals of ZnO from the base of the flowerets. Free-standing ZnO nanorods have a mean aspect ratio of 8.5 ± 4, where the length and average diameter are ∼356 ± 64 nm and 42 ± 16 nm, respectively, and the specific surface area of 12.5 m2 g−1 with an increment of ∼650% as compared to the mechanically alloyed powder particle. © 2018 The Society of Powder Technology Japan