Gosh, you're lucky. I struggle to keep such plants I bought and planted nearby alive.
You should plant some, or spread the seeds in the fall.
They're not just perennials, but some spread far (some just clump) via the roots.
One common milkweed that sprouted from seeds I tossed 2 years ago came up round 5 plants the next and started to flower, this year it's a mini forest. This is in a parkway nearby at the edge of some woods, and they hadn't mowed in 2 years because they were replacing sewage pipes, so hoping next year they won't mow too much down when they resume that. Parks Dept here are imbeciles, killing natives but leaving invasives grow.
There's a nursery called Missouri Wildflowers that sells an assortement of native milkweeds (and other species) with different habits as cheap as they get. Planting various has the added bonus of different flowering periods, so as one ends, another begins, and you're feeding pollinators for an extended season.
Have to be careful with placement, because other than Asclepias Tuberosa and that tropical one people sometimes plant, they're a bit big and course for the formal garden and as I said, can ovetake an area.