Bernard McMahon

Today is the birthday of the Irish-born botanical steward of the plants collected by Lewis and Clark; the Philadelphia nurseryman, Bernard McMahon, who was born on this day in 1816.

McMahon's lasting legacy was his American Gardener's Calendar. Packed with monthly directions and information about all things gardening, McMahon's Calendar was the most popular and most comprehensive gardening publication of the first half of the nineteenth century. Through his work, McMahon was helping to shape the gardening identity of America, which was becoming more distinct and defined as it transitioned away from English traditions. The Calendar was like a gardening bible to Thomas Jefferson, and it was that connection that led McMahon to become his gardening mentor. It also meant that when it came time for Jefferson to pick a curator for the Lewis and Clark expedition, McMahan was his pick.
Lewis and Clark are forever remembered for their famous expedition, which led to many botanical discoveries. The live plants and the seeds they had collected were expertly curated by McMahon, who didn't dither, especially with the seeds. Once the specimens were in his hands, he immediately set about cultivating them. 
There were constraints placed on McMahon. As the sole nurseryman fortunate enough to steward the collection, he could not propagate the plants for profit (they were the property of the United States Government) and he could not tell anyone about the collection (at least not until Lewis and Clark had a chance to write about it).
In honor of his work, the botanist Thomas Nuttal named the genus Mahonia for McMahon. Mahonia is an evergreen shrub, also known as Oregon holly. The low-growing shrub can be kept tidy with pruning and looks like holly, although it belongs to the barberry family. The Mahonia produces yellow flowers followed by clusters of bluish-green berries that turn red in the fall. The red berries attract birds, and gardeners love that it is a favorite of cardinals. Mahonia has a glossy, dark green foliage that turns a gorgeous bronze in autumn.