Purple milkweed season

Purple milkweed (Asclepias purpurascens), a State Endangered Species, is at peak flowering right now. This plant, a characteristic savanna indicator species, first appeared spontaneously at Pleasant Valley Conservancy after we did some initial clearing followed by a prescribed burn in a white oak savanna. As we continued to restore more savanna areas, more purple milkweeds cropped up.

Once pod formation occurred, we collected seeds and raised plants for transplanting. We have also thrown out seed in likely areas. We now have over 40 sites where this species is growing, some native and some from transplants.

Every year we have one or two new spontaneous appearances. This year we had two, of which one is shown in the photo. (Note the grapevine intertwined. After taking this picture, I spent a few minutes carefully cutting it away from the milkweed stems.)

How can we tell a spontaneous plant from one arising from seeds we threw out? The two new stands this year both are right next to trails, in places we never would have thrown seed. Apparently, seed continues to get around on its own.

This is a perfect time to find new flowering areas, because they stand out so well, even when growing among other savanna forbs. I always do my surveys for new populations in the middle of June, which is peak flowering time for purple milkweeds.

I published a paper last year in Ecological Restoration on ecology and conservation of purple milkweeds, which describes "tricks" we have developed for raising plants and getting them to grow in the field. You can find a PDF of this paper on the Pleasant Valley Conservancy web site. If you type "purple milkweed" in the Search box for the PVC site, this PDF should come up at the top of the list.