Asclepias syriaca	Asclepias incarnata
plant with a single stem, wide leaves	plant with clump-forming stems, narrow leaves
inflorescence with pink, white and purple flowers	inflorescence with white flowers (cultivar), wild species with pink flowers
corona filaments as long as corona	corona filaments longer than corona
warty seed pod, never upright	pod upright and smooth
Photos A. syriaca flowers: J. Schaminée-Sluis