Following the Russian occupation of the Amur River region in 1850, several exploratory missions were sent along the great river. Richard Maack, a young Russian naturalist, was attached to one of these in 1855. Born in 1825 at Arensburg on the Baltic island of Oesel, he had studied natural sciences at the University of St. Petersburg. He was subsequently appointed to a teaching position at a grammar school in Irkutsk. He was later the school's director and then Superintendent of Schools in eastern Siberia (1868-1879).

On a hiatus from his role in Siberian education, Maack left Irkustk with the exploratory expedition in April 1855, boarding a great raft on the river in May. The party remained travelling by water until November, when the river froze, and horses were used instead to explore the river valley. Among the places the explorers stopped were Albazin, Marinsk, Aigun and Ust Strelka. Maack made frequent stops to collect plants and zoological specimens. Maximovicz described the plants in his Primitiae Florae Amurensis and Maack published an account of the trip, Journey on the Amur (in Russian) in 1859.

Three years after Maack had returned to Irkutsk in January 1856, he was commissioned by the Siberian branch of the Imperial Geographical Society to explore the Ussuri valley. Completing this expedition in 1859, he published his observations of the area in two volumes, the second one devoted entirely to the Ussuri flora.

Sources:
E. Bretschneider, 1898, History of European Botanical Discoveries In China: 612-616.