Synchronizing male and female flowers in hybrid maize (Zea mays L.) seed production is critical for maximum yields of high quality seed. Many factors may delay planting in a particular region beyond the optimal planting time, creating a different temperature and photoperiod environment interacting with a female and male maize inbred pair. Maize ontogeny is controlled by temperature and photoperiod, although publications disagree on the magnitude of impact these factors have. The transition of the shoot apical meristem (SAM) from vegetative to reproductive growth in maize it is called tassel initiation (TI). TI is always preceded by an accelerated expression of the ZCN8 gene, regardless of the photoperiod conditions. ZCN8 expression patterns were successfully used to detect tassel initiation of thirteen temperate maize inbreds under different environmental conditions, characterizing vegetative and reproductive time by inbred at all locations.