Despite the location of this photograph (Le Jardin des Plantes, Paris), Asclepias incarnata, or swamp milkweed, is native to much of eastern and central North America. As its common name implies, it is typically a species of wet meadows, wet ditches and marshes, which is somewhat atypical for the species in North America; I associate many of the other species with well-draining soils or dry locales.
Asclepias incarnata makes for a good addition to gardens, where it is useful as a nectar-source for butterflies. It is also a larval host for monarch butterflies, though not as preferred as other species in the genus. Several cultivars are available, including a white-flowered selection (see the Wikipedia entry for additional photographs of the species and some cultivars: Asclepias incarnata).
On a personal note, thank you for the well-wishes everyone. I hope all BPotD readers are able to celebrate togetherness and reflect on 2012 over the next while. Myself, I’ll be raising a glass to several people who passed away this past year. All were readers of BPotD or personally interested in my photography, and all continue to inspire me.