morphogenesis of a branching structure secondary shoot formation auxiliary shoot formation The process that gives rise to secondary (or auxiliary or axillary) shoots in plants. This process pertains to the initial formation of a structure from unspecified parts. These secondary shoots originate from secondary meristems initiated in the axils of leaf primordia. Axillary meristems function like the shoot apical meristem of the primary shoot initiating the development of lateral organs. biological_process GO:0010223 axillary shoot system formation axillary shoot formation shoot branching shoot axis formation