Perennial ryegrass (Lolium perenne L.) is a grass species that is widely sown on dairy and sheep farms in temperate regions owing to its persistence and capacity to produce high amounts of herbage that is rich in nutrients and metabolizable energy. However, when ryegrass plants transition to flowering in spring, there is a sharp decline in digestibility and metabolizable energy content. To address this, breeding efforts have aimed to delay the onset of flowering, however late flowering poses problems for seed production. The goal of our research is to develop a ryegrass cultivar that does not flower on farms in temperate regions, and is thus able to maintain high levels of metabolizable energy into summer, but can still be induced to flower for seed production. As a first step, we developed a scalable pipeline using long-read amplicon sequencing for routine haplotype analysis in perennial ryegrass populations. We applied this technique to survey the key genes in the flowering pathway in several F2 accessions generated from crosses between various New Zealand commercial cultivars and European ecotypes. These plants were found to segregate for extremely late heading (≥ +35 days) over several seasons, allowing us to compare sequence variation with flowering behaviour. Furthermore, extremely late flowering plants could be induced to flower earlier by altering the duration of photoperiod. The identification of the candidate flowering pathway gene variants contributing to extremely late flowering will be invaluable in the breeding of an elite non-heading perennial ryegrass.