Pennsylvania–M’Mahon came from Ireland in 1796 and began to collect and
export seeds of native American plants in 1800. His catalog of 1804
listed seeds of about 1,000 species. In 1806, he published his book
American Gardener’s Calendar, that was for 50 years the standard gardening
authority in America. There were eleven editions of his book by the
last edition published in 1857. A general catalog of garden plants
was published at the end of the book. He knew Jefferson and his store became
the meeting place of botanists and horticulturists. M’Mahon
helped to distribute the seeds collected by the Lewis and Clark Expedition.
M’Mahon died on September 16, 1816.
Sources: Plants; Woodburn2;
CHSJ-Apr. 1966; Leighton1;