Most everyone has broken open a milkweed seed pod and watched as the hundreds of seeds, with their fuzzy attachments float away. Very important plant to the Monark Butterfly.
The references list it as full sun to shade. I have seen it mostly growing in full sun.
Soil & Site
I have seen it growing on the sandy shores of Lake Superior and in the open fields of southeastern Wisconsin.
The lavender to pink, purple flowers form a somewhat drooping dome. They are pollinated when the insects visit the plant and get the pollen sacs stuck to their legs.
Bust off a leaf and it will bleed a sticky, toxic sap.
Listed as reaching 2-5 feet. I have seen them mostly in the 2-3 foot range.
South Canada and south
The milky sap of this plant contains cardiac glycosides, which is not good to ingest. The Monarch Butterfly lays its eggs on this plant and than the larva eat the milky sap and become toxic to other animals that may eat it. Some birds use the fibers from old plants as nesting material.
Notes & Reference
#08- Peterson's Guide to Wild Flowers (Peterson McKenny), #41-Wildflowers of Wisconsin (Stan Teikiela)