Field plant mapping data over two seasons were analysed to determine the best sampling location for analysing FD. The results showed that the mid flowering stage provided the best and most reliable distinction (P < 0.05) between genotypes for FDfin, which averaged 189 mm−2. The ranking for genotypes at early and late flowering stages varied across seasons, such that genotype differences were reduced or not significant at those stages. FDfin at the early flowering stage was 170 mm−2, as seeds had greater SSA compared with seeds from flowers from mid and late stages, due to plant competition and less favourable climatic conditions.