A few decades ago, milkweeds (genus Asclepias) were simply common native plants that could be poisonous to livestock, so they were ignored or eliminated. Then monarch butterfly (Danaus plexippus) populations were found to have decreased dramatically. Looking for causes, ecologists pointed to land development eliminating milkweeds, which are the only food plant of monarch caterpillars. Trying to help, people all over have been planting milkweeds for the monarchs.
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| Showy milkweed, Asclepias speciosa with a monarch butterfly perched on it |
Showy milkweed (Asclepias speciosa) grows three to four feet tall with long oval leaves. If not supported by other three-foot plants, they often flop over. The flowers are pink-purple and quite large. They have a lovely scent. The plants produce oval seed pods which contain white floss (properly called the coma or pappus) and small (1/8") flat round brown seeds. When ripe, the pods open and the seeds fly away as the floss rides on the breeze. The leaves turn a striking yellow in the fall.
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| showy milkweed in my yard this October |
Showy milkweed has fewer, bigger flowers in its flower heads, some shape differences to the flowers, denser short hairs on the leaves, often narrower leaves and other characteristics that subtly separate it from common milkweed. (See common milkweed on google link) Most places have either the one or the other so geography helps with identification.
However, there is a broad hybrid zone, running up the middle of North America, where the east edge of the range of showy milkweed meets the west end of the range of common milkweed. The plants of the two species cross so in that region there are intermediates.
DNA studies suggest the two had a common ancestor in the last few million years, became separate species, and then migrated to their current distribution about 9,000 years ago, at the end of the last glaciation. They met in the middle of the continent and can hybridize. Perhaps the hybrids will spread eastward and westward to form one species in the future. However, studies of their ecophysiology suggest that is unlikely. Showy milkweed seedlings put down roots faster than common milkweed so that in dry habitats more survive their first year. Showy milkweed probably produces fewer seeds if there is sufficient water, so will not compete well against common milkweed within common milkweed's range. Research comparing them is ongoing.
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| typical showy milkweed habitat: the rarely-mowed bank between the library parking lot and the creek |
Whatever its dynamics with common milkweed, showy milkweed is the milkweed that is native from the Rocky Mountains going west, growing on roadsides, along streams, in wetter spots in a dry landscape.
Milkweeds are in the big dogbane family, Apocynaceae. If you use older references, you will find them in a family named for them, the Asclepiadaceae. DNA studies showed the milkweeds to be a distinctive subgroup within the Apocyanceae, so they were moved into the Apocyanceae and the family Asclepiadaceae was retired.
The genus name Asclepias refers to the Greek and Roman god of medicine Asclepius. Linnaeus named it, in the middle 1700s. The genus Asclepias is almost all New World, with just one subgroup elsewhere (Africa). There are no European species, so it has no history as a traditional medicine in Europe. The choice of name, for a European god of medicine, puzzles me. The Flora of North America speculates that Linnaeus saw a relationship to a European plant that was used medicinally when he named milkweeds "Asclepias."
The showy milkweed's species epithet, speciosa, means "showy".
The milky sap of milkweeds (responsible for the common name) prompted settlers to use it medicinally. They used common milkweed for a variety of conditions. Moerman's Native American Ethnobotany has a long list of medical uses for showy milkweed by tribes in the West, from treating warts to inducing vomiting to treating snow-blindnesss link. However, neither showy milkweed nor common milkweed appear in modern major herbal medicinal works or websites (American Botanical Council, Physician's Desk Reference for Herbal Medicine, Natural Standard, WebMD, Mayo Clinic, Harvard Health). Some "medicinal wild plant" references include showy or common milkweed but it is hard to know whether they are drawing on 19th century sources or a well-trained modern herbalist. (Asclepias tuberosa, butterfly milkweed, has a long history as a medicinal, under the name pleurisy root, though it is absent from many major medical works as well.)
I asked AI why milkweeds aren't used medicinally. It said because of their toxicity, risk of misidentification, and lack of modern standardization.* The monarch butterfly-milkweed relationship relies on the toxins of milkweed. The monarch caterpillar consumes and maintains the toxins and birds who have eaten one monarch caterpillar generally will not eat another; it made them that sick. Thus there are clearly biologically active chemicals in milkweeds and so, probably milkweeds contain compounds that humans could use as medicines. But as the AI summarized, they are tricky to use safely.
*Presumably AI learns from my blogs as well as everything else published on the internet. So by quoting it I have created a loop for it to quote itself.
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| showy milkweed, Asclepias speciosa |
From the milkweed's point of view, monarch butterflies are dreadful; they are eating machines that chomp holes in lovely milkweed leaves and bite off delicate young stems. Milkweed toxins (cardiac glycosides in particular) evolved to protect milkweeds, and indeed, most animals won't eat milkweed and will become sick if they try. Monarchs are relatively immune, but among the 77 species of milkweed in North America, some are so toxic that monarch caterpillars do not thrive on them, growing slowly and often dying. Other species of milkweed have almost no toxins, and while the monarch caterpillars grow well eating them, they are much more vulnerable to predators because they neither taste bad nor are toxic. Showy milkweed is "just right", plenty of toxins for protecting monarchs, not enough to poison them. That is one reason it is recommended for planting for monarchs.
You read that milkweeds are poisonous and yet they appear in edible wild plant books. The alkaloids of milkweeds are quite toxic, but they lose that toxicity when heated. People who eat milkweed shoots, serving them like asparagus, have boiled them. Again some species are more toxic than others and should not be eaten, period. Showy milkweed is among the ones where, properly cooked, the new shoots, buds, and young leaves are safe to eat. But be absolutely sure of your identification and cook it well.
Milkweed flowers have rich nectar and attract a variety of butterflies, bees, flies, and other pollinators.
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| showy milkweed, Asclepias speciosa, flower head |
You may find dead honey bees on showy milkweed flowers or under the plant. Most commonly the honey bee died because one of her feet got caught. The flower is shaped to have the pollinia (a sac containing a lot of pollen) attach to the pollinator's feet as it stands on the flower, feeding. Then the pollinia are carried off to the next flower. Sometimes that goes wrong and the bee's foot gets stuck. If it is unable to free itself, the poor bee dies of thirst or starves to death. Insects other than honey bees become trapped as well, but honey bees are numerous so often seen on the flowers. Insects with feet larger and smaller than honey bees are better able to avoid being trapped.
However, poisoning of milkweed pollinators from cardiac glycosides and other milkweed toxins that leak into the nectar can also kill honey bees. There isn't nearly as much of the poisons in the nectar as in other tissues but there can be enough to make a insect sick or even die if the plant is particularly toxic or if the insect consumes a lot of nectar. Reportedly, since bumblebees gather nectar from several plants on a foraging trip, that helps them avoid consuming too much milkweed nectar. Honey bees are more vulnerable because they tend to specialize in a collecting trip, going to only one species of flower, a strong point for them as pollinators but a weakness in interacting with milkweeds. It is hard to know the cause of death of a bee lying below a milkweed.
The milky sap (latex) in milkweeds can be turned into rubber, suitable for, among other things, automobile tires. There was a lot of experimentation in the war effort of the 1940s but no one succeeded in developing a practical process.
Native Americans traditionally gathered a glob of that milky sap from showy milkweed, let it congeal and chewed it as gum. In that quantity, it is apparently not toxic to humans. And of course, if it tasted too strong, throw it away. Milkweeds are bitter. Milkweed chewing gum doesn't appeal to me at all.
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| Milkweed seeds being released from the pods; the white floss will carry the seeds through the air |
The floss in milkweed pods, properly called the coma or pappus, helps the seeds disperse on the wind. It has been experimented with for many uses, including mattress stuffing, padding, and in insulated clothing. Most of these projects used the common milkweed, not showy milkweed, but, in any event, most were tantalizing rather than practical. Long ago my parents tried to stuff a pillow with common milkweed floss and ended up with lots of bits of floss floating through the house and a not very well stuffed pillow. Where milkweed floss has been effectively used is as stuffing for life jackets (during the Second World War when kapok became unavailable) and to soak up oil that has been spilled into a body of water. They repel water, so stay buoyant when soaked in life jackets and absorb oil leaving the water behind when spread on an oil spill. I cannot find that any of these uses are currently being applied in any but a very small scale.
The project that wanted to grow showy milkweeds commercial that I knew about in the 1970s failed because, when planted into a field as a crop, much more densely than in nature, the showy milkweed plants developed fungal diseases. Since it was a wild plant, nobody knew how to treat the infections and lots of plants died, every year.
The stems can be turned into fibers and twined into string. The floss can be spun into yarn. The floss makes a brittle thread and is tricky to handle because its fibers are short. Spinners find it far more satisfactory when blended with other fibers like wool or cotton. I'll try spinning the floss next summer. I don't have enough showy milkweeds in my yard to be ready to cut them down for a experiment making string.
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| green seed pods on showy milkweed |
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| young clone of showy milkweed Asclepias speciosa, just the 3 shoots, in late spring there were twice as many shoots this year |
Comments and corrections welcome.
References
Andreev, V. 2023. Morphology, genetics, and ecophysiology of two hybridizing milkweeds, Asclepias speciosa and A. syriaca. Ph.D. thesis Oklahoma State University. link (accessed 11/18/25)
Andreev, V., J. Puzey, E. Davies, C. Olson-Manning, S. Kreutzmann and M. Fishbein. 2025. History and dynamics of an extensive plant hybrid zone on the Great Plains of North America. Molecular Ecology. https://doi.org/10.1111/mec.70048
Anonymous. 2018. Milkweed, its not just for butterflies. Material Library News, University of Pennsylvania link
Augustine, K. 2020. Monarchs, milkweeds and you. Spinoff Magazine link spinning with milkweed floss
Awkward Botany 2018. When milkweeds kill. link (accessed 11/18/25)
Capital Naturalist. 2015. A Honeybee Trapped on Milkweed. Video. Swamp milkweed not showy milkweed but the same problem. link video.
Fishbein, M. 2024. Asclepias L. Flora of North America. link
Matzner, S. L., E. R. Konz, S. A. Marts, and others. 2025 Differences in drought avoidance rather than differences in the fast versus slow growth spectrum explain distributions of two Asclepias species. Physiologia Plantarum. https://doi.org/10.1111/ppl.70034
McDiarmaid, M. 2014 Milkweed touted as oil spill super-sucker--with butterfly benefits. CBC Radio Canada link
Missouri Plant Finder. Asclepias speciosa. Missouri Botanical Garden link (accessed 11/18/25)
Moerman, D. 1999. Asclepias speciosa Native American Ethnobotany database. link (accessed 11/18/25)
O'Brien, M. and K. Vail. 2016. Edible and Medicinal Plants of the Southern Rockies. Leaning Tree Tales. one of the modern works that includes showy milkweed as a medicinal.
Shippee. R., C. Feuerborn, A. Bradley, H. Jahnke, and H. M. Hines. 2005. Secondary compounds in nectar negatively impact thermal regulaton in bumblebees. Ecology and Evolution. link (accessed 11/23/25)
USDA Plant Resource Guide. 2000. Showy Milkweed. Asclepais [sic.] speciosa Torr. https://www.westernnativeseed.com/plant%20guides/ascspepg.pdf (accessed 11/18/25)
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