Butterfly milkweed, Asclepias tuberosa
 
The bright orange butterfly milkweed is everyone's darling.
This relatively short plant, only 30 to 90 cm, is ideal for borders. The showy orange flowers bloom from June to August. The plant emerges later than most other plants but then grows very rapidly. In May, nursery plants will often not have emerged or will be very small. It is better to transplant plants when they have had some time to photosynthesize and put some energy into their root system.
 
Ecology:
Milkweed is the only plant that monarch caterpillars can feed on. Butterfly weed is also a host plant for queen butterflies, moths and milkweed beetles.
Milkweeds are always buzzing with activity. Their rich nectar is a favourite of many butterfly, bee, wasp, fly, and beetle species. 
 
Growing conditions:
In the wild, butterfly milkweed occurs in sandy oak savannas, old fields, prairies, hillsides, roadsides, and open woodlands. It needs well-drained, medium-to-dry soil and thrives in full sun. Butterfly weed thrives in sandy soil and gravel, but sometimes even clay.
Butterfly milkweed develops a long taproot and, therefore, will be drought tolerant once established, but hard to transplant. 
Butterfly milkweed can be a bit finicky even in a perfect spot, but it can also surprise you. My butterfly milkweed has been growing for many years on an east-facing slope in clay soil covered with heavily compacted construction site dirt in partial sun - against all odds.