Common milkweed (Asclepias syriaca)

Common milkweed , the bane of farmers and bean walkers!  However, it is a staple in a monarch's diet, and in my research plot this summer, had the second highest count of monarchs, with 30 total: 19 eggs and 11 larva.  In the prairie, you can see how tall this milkweed will grow, if you notice there is another common milkweed over my left shoulder in this photo taken at Neal Smith National Wildlife Refuge.

This perenniel grows from deep rhizomes, so once it's established, I'll need to control its spread in my flower bed.  Here is a fifth instar preparing to form a chrysalis on August 15th.  Notice that the common milkweed's elliptic leaves are fuzzy, particularly on the underside.  

On August 16th, the caterpillar had formed a chrysalis.

When I approached the plant on August 30th, a monarch butterfly flew off the plant.  Usually adults emerge in the morning and it takes most of the day to inflate and dry its wings so it can fly. Notice the reddish fluid (called meconium) on the leaf below:  that is leftover metabolic waste that was expelled after the butterfly emerged.