That is tropical milkweed. I usually buy seeds and start indoors and treat as annuals (I've never seen them in garden centers). They grow to 3-4 feet tall and bring in lots of monarch caterpillars, and other butterflies and hummingbirds love the nectar. They look best in clusters. Rabbits and deer will not touch it.
I get lots of chrysalises from late July through mid-Sept, and find them hanging on fences, siding, tops of doorways, etc. They are like clock-work once they make the chrysalis, almost always hatching 10 days later. I usually bring chrysalises I find outside in so they can hatch safely. I've gotten good at getting them down -- I wait until they've hardened a little (couple days), and spray them with a little water, then carefully pull off with the webbing material they attach with. I also sometimes I'll bring in a dozen or so cats to let them make their chrysalises inside.
Oh and lantana is a great butterfly attracting plant. Low maintenance and deer/rabbit proof. Here are some pics from last year:
Just hatched on the deck:
Bunch of chrysalises in an aquarium:
Tropical milkweeds in a cluster: