This dedication allowed him to continue his studies at the Universidad Nacional de Trujillo (UNT), where he would eventually achieve the degree of doctor of biological science in 1976.
[6] "Como quisiera que el sol se estacionara para seguir trabajando" How I wish the sun would stay in place so I could keep on working.
Alongside his teachers Nicolás Angulo Espino and Arnaldo López Miranda, which he greatly admired (he named after the later a genus and the journal he founded) and constantly referred to both in daily life and teachings, he is thought of as a pioneer of botany in Northern Peru.
[1][2] Until his postdoctoral work in La Plata, Argentina under Ángel Lulio Cabrera in the late 60s,[1][2] Sagástegui had been interested primarily in Cyperaceae, with some forays into pteridology.
By the time he obtained his doctorate, however, he had cemented a reputation as a specialist in the Asteraceae with over a dozen species to his name, mostly in Coreopsis and Verbesina.
He would over the course of his career describe four new genera (Caxamarca, Jalcophila, Parachionolaena and Pseudoligandra) and nearly a hundred species in total, almost all of them composites, with 30 more named after him.