Zinc oxide pompom-like particles were crystallized by heating solutions of zinc amino complexes in open air. The nature of the precursor (nitrate, hydroxide or a mixture of both) changes the precipitation pH and the growth mechanism, involving in the case of nitrate salts ramified branches and stratified tips, whereas hexagonal rods with flat ends grow from zinc hydroxide precursors. (c) 2005 Elsevier B.V. All rights reserved.