Nikolaj Eeg Kruse Hartz (23 August 1867 – 7 May 1937) was a Danish geologist and botanist.
He graduated in 1895 and obtained a Ph.D. in 1909 with a dissertation about the late-glacial flora and fauna of Denmark.
Together with his colleague Vilhelm Milthers (1865–1962), he investigated a clay pit near Allerød in Denmark and found that a period with milder climate and birch forest – the Allerød oscillation - had interrupted the cold and dry Dryas stadial (Hartz & Milthers 1901).
[2] [3] [4] In 1913, he abandoned his scientific career and became co-director of his brother's firm, Standard Mønsterforretning which had been established in Kristiania, Norway in 1900.
[6] The grass species Poa hartzii was described by the French botanist Michel Gandoger (1920), who named it after Hartz because it was based on plants collected by Hartz in "Kordlunguak" at the Sullorsuaq Strait, West Greenland.