Peter Nielsen (botanist)

Peter Nielsen (28 July 1829 – 30  September 1897) was a Danish botanist and plant pathologist.

He was born at a farm in Vonsbæk parish in the Duchy of Schleswig. He graduated in 1857 from Jelling Statsseminarium in Vejle. He was employed at Flakkebjerg Institute from 1857-1859. In 1859, 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.