He began to study botany at the Ludwig Maximilian University of Munich but due to the start of the Second World War he joined the German army and was assigned to an intelligence unit in Russia.
After illness and time as a prisoner of war of the British,[2] he returned to university study in 1946 and graduated with a bachelor's degree in natural sciences in 1950.
He made use of the lichen herbarium at the university's botanic garden which contained nineteenth century specimens collected by Ferdinand Arnold and August von Krempelhuber.
[3][4] In 1965, Poelt was appointed to the chair in Systematic Botany and Plant Geography at the Free University of Berlin to lead a new research institute.
[3] He was able to develop an international centre for cryptogam biology that included visiting researchers, an extensive herbarium and training programmes.
[4] He also travelled widely to see lichens in the field, including to Brazil, Costa Rica, Greenland, Tierra del Fuego, Pakistan, Afghanistan and Nepal as well as all round Europe.
[6] It was followed by a number of exsiccatae distributed through the University of Graz, among them, starting in 1977, the series Reliquiae Petrakianae with plant material collected by Franz Petrak.
[4] The book Bestimmungsschlüssel europäischer Flechten was published in 1969, an important key for identification of European lichens, followed by several supplements (1977, 1981) that he prepared in collaboration with others.