Purple milkweed, Asclepias purpurascens
 
WOW, what a milkweed! Purple milkweed has showy red-purple flower clusters and blooms for a long time from June until August.  The flowers are big and beautiful, similar to common milkweed, but the flower umbels don't droop but are upright. It also doesn't spread aggressively by rhizomes like common milkweed does. The opposite is true; it is rather hard to establish.
Purple milkweed is listed as a rare plant in Ontario that will hybridize with common milkweed.
 
Ecology:
Purple milkweed is the host plant for the monarch butterfly and a sought-after nectar plant for various bees and butterflies.
 
Growing conditions:
It naturally grows in full to partial sun on woodland edges, in dry open woodlands (oak and oak/pine forests), on sandy soils of prairies, in dry fields, shrub thickets, and lakeshores, as well as in wet prairies and calcium-rich sites.
In the garden, purple milkweed does best in light shade and moist, well-drained soil or in full sun with additional deep watering.  Purple milkweed is endangered in many counties in the States and rare in Ontario. It is finicky to get established, as it has high nutrient requirements and might go dormant for a year to pop up the following year.