Asclepias physocarpa

Asclepias physocarpa (also known as the swan plant, balloonplant, or balloon cotton-bush) is a species of milkweed plant. It belongs in the subfamily Asclepiadoideae.  It has been naturalized in Hawai'i and has also been naturalized in other parts of the world.

Other websites

Asclepias physocarpa at USDA PLANTS Database

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