Peter Nielsen (botanist)

Peter Nielsen (1829–1897) was a Danish botanist and plant pathologist. He was born at a farm in Vonsbæk parish in the Duchy of Schleswig. He became a school teacher at Ørslev in Zealand, where he studied the local flora. He was particularly interested in plants useful to agriculture and in plant pathogens. He was a prolific writer on these topics. He undertook meticulous studies of rust fungi. He was the first to describe the host alternation of Puccinia poarum between grasses and Tussilago farfara.