Many if not most native prairie plants make seeds that require exposure to winter weather in order to become viable and germinate in the following spring. I'm not sure about common milkweed, but I know from experience that Asclepias tuberosa, aka butterflyweed, belongs in this group. One way to accomplish this is to collect the seed pods in late fall, say mid-November, and let them dry out thoroughly for a month or so. Next they go into a paper bag, so they have some fresh air, and they are put outdoors onto a porch or some location protected from rainfall, where they sit all winter. In the case of A. tuberosa, the seeds can be planted in early spring, say mid-March, and the pots should be placed outdoors where they are exposed to freezing nights and sunny days. It will take 2 or 3 months, but eventually, most of the seeds will germinate. One year I had to wait until early July, but they finally sprouted.

I was planning on wintersowing them, so they will get moist cold that way. But I don't want to bring the pods in to dry too early. I'm afraid they won't ever mature if I take them off the plant too soon.

I usually leave the pods on the plant until they just begin to split open. We have A. tuberosa, A syriaca, and A incarnata. None of our milkweed pods have split open, but I suspect that the seed is pretty well developed at this point.

My physocarpa, incarnata, tuberosa, and curassavica have all begun to ripen and split. I've harvested several seeds. I almost have no incarnata pods left and this was a very prolific year for them. The physocarpa is still covered abundantly with pods but all are beginning to darken so I'm watching closely so I can harvest.

`Laura

Laura,

I took late cuttings of physocarpa late last year for a table centerpiece and was pleasantly surprised when two seed pods split open with mature seeds a couple weeks later...I'm sure you still have plenty of time down south for them to develop though. Tony

How can you tell if the seeds are mature? In other words, if you bring the pod in before it has split, and it splits later, how can you tell if the seeds are viable? And if a frost hits, and the pods are still green, will they still mature?

A frost may help the large green pods ripen. Yellow pods brought in and allowed to split a few days later are fine, as long as the seeds are brown and intact.
Of course, very young pods may suffer, but large, green pods will actually benefit from a light frost.

undeveloped seeds will be a white or yellowish color while the mature seeds will be brown. You'll know the seeds are mature when the pod starts to split open naturally.