Asclepias speciosa

Identification

Gallery

Description

Showy Milkweed is a perennial, with three foot tall stems and large gray five inch leaves, fruits 4" horns, flowers compound 4-5" cluster like a Forth of July firework. In our area Asclepias speciosa is covered with monarch caterpillars during the summer. The Orioles use the dead stems for nests the next spring. (The matter looks like fiberglass.) Asclepias speciosa is similar to Asclepias eriocarpa , but taller and less fuzzy leaves, and much more fragrant, the petals are the color called antique or Victorian rose. One plant can form a large clump by its spreading rhizomes. It needs sun. It is quite drought tolerant,(not in the same league though as Asclepias A. eriocarpa, erosa or californica ) plant, water well first summer and ignore. Tolerates alkaline soils and most gardens. Needs cross-pollination for fruit and seed development. Pollen is self-incompatible.
The alkaloids associated with this milkweed and other milkweeds give the monarch and other butterflies that feed on it protection from predators. Alkaloids from the wrong milkweed (South American, Mexican, etc.) can expose the butterflies to predation. If the monarch or other butterfly has not evolved with the milkweed they may have limited tolerance for the particular alkaloid or latex of the plant species. The California flyway runs from Baja to Canada, it does not include Mexico proper nor Central America. If you live in Chicago you can plant Mexican species (Asclepias mexicana) or Asclepias tuberosa, don't plant our species. You might look at the Monarch entry in James Scott's Butterflies of North America and articles by Fink, L and L.P. Brower.
I would guess the symptoms to be similar to the problem of intolerance to legumes that some people have. syn. Asclepias douglasii, Asclepias curvipes .