Common Milkweed, Butterfly Flower, Silkweed, Virginia Silkweed

Asclepias syriaca

ass-KLE-pee-us  seer-ee-AK-uh

Synonyms of Asclepias syriaca (15) (Updated on 11-12-22 from Plants of the World Online): Asclepias apocinum Gaterau, Asclepias consanguinea Kunze, Asclepias cornuti Decne., Asclepias fragrans Raf., Asclepias globosa Stokes, Asclepias grandifolia Bertol., Asclepias illinoensis Michx. ex Steud., Asclepias intermedia Vail, Asclepias obtusifolia Kunze, Asclepias pubescens Moench, Asclepias pubigera Dumort., Asclepias serica Raf., Asclepias syriaca f. inermis J.R.Churchill, Asclepias syriaca f. leucantha Dore, Asclepias syriaca f. polyphylla B.Boivin

Asclepias syriaca L. is the correct and accepted scientific name for this species of Milkweed. The genus and species were named and described as such by Carl von Linnaeus in the first volume of the first edition of Species Plantarum in 1753.

As of 11-22-22 when this page was last updated, Plants of the World Online by Kew lists 205 species in the Asclepias genus. It is a member of the plant family Apocynaceae with 369 genera. Those numbers could change as updates are made on POWO.

The above distribution map for Asclepias syriaca is from Plants of the World Online. Areas in green are where the species is native and purple where it has been introduced. The map on the USDA Plants Database for North America is similar.

The map on iNaturalist shows where members have made observations. Anyone can join and it is a great website to confirm and share your observations. The maps on iNaturalist and continually updated as members post new observations.

THERE ARE SEVERAL LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING AND TO HELP WITH A BETTER POSITIVE ID.

The Asclepias syriaca, Common Milkweed, has been growing by the lagoon here on the farm for several years. In 2019 I noticed it coming up in the main pasture and in the back of the farm. It doesn’t really have a chance to grow well in the pasture and hayfields because they get eaten or mowed off before they flower (even though they come back fast). The photos from July 12, 16, and 19 in 2019 were taken on a friend’s farm. This species grows fairly tall.

I took A LOT of photos

 

 

As with all milkweeds, their stems and leaves contain a milky sap that has variable toxicity in the form of cardiac glycosides.

The stout stems are densely hairy (densely pubescent) but sometimes hairless (glabrous). They are usually unbranched below the inflorescence (flower stems).

 

The leaves grow in an opposite manner along the stems and are up to 8” long x 3 1/2” wide. Leaves are described as being broad, oblong or elliptic-ovate, rounded or pointed at the tip. The midribs are usually purplish toward the base. The upper surface is usually hairless but can have very fine, short hairs. The undersides of the leaves usually have very fine, short hairs…

 

The above photo shows the stems with fine hairs giving it a chalky appearance.

The veins of the leaves grow outward from the midrib toward the leaf margins.

View from the top showing the opposite arrangement of the leaves.

The rest of the photos were taken on the farm where I live… There is a good-sized patch next to the lagoon and surrounding area. They are also scattered along the south side of the farm from one end to the other and along the street in front of the pasture.

The Asclepias syriaca have been growing on the bank of the lagoon for several years. Now they are growing in the fence row and pasture in front of it. Even though I mow around the lagoon every week during the summer, I haven’t photographed their flowers…

Unlike most other Milkweeds, Asclepias syriaca have these distinct seed pods with tubercles…

Hmmm…

<<<<2020>>>>

Starting to bud…

Umbels of flowers grow from the upper leaves… I am running out of words. There are better descriptions below of the flowers…

 

No matter when it is, the Milkweeds always have insects of some kind somwehere on the plants…

 

 

<<<<2021>>>>

The above photo is of a colony of Asclepias syriaca in the southeast pasture.

The above photo and the next four were taken of a small colony along the fence outside of the front pasture.

Typical of Milkweeds, the flowers grow in globose umbels, 2-10 per stem, emerging from the axils of the upper leaves. The umbels contain 20-100 flowers.

Flowers are about 1/4” across, with 5 reflexed petals (corolla lobes), 5 raised hoods with curved horns… You can read the descriptions on the Missouri Plants website for much more technical descriptions… Pollination is quite interesting with all milkweed species. There are several links at the bottom of the page with very good descriptions.

These plants by the fence flowered earlier than the rest of the plants on my farm…

 

 Flowers are about 1/4” across, with 5 reflexed petals (corolla lobes), 5 raised hoods with curved horns… You can read the descriptions on the Missouri Plants website for much more technical descriptions… Pollination is quite interesting with all milkweed species.

The above and below photos are of the same plant along the south hayfield.

Asclepias syriaca have fruits and seed pods similar to other Milkweeds except that they are covered with narrow warty tubercles… Seeds are distributed by wind with their soft fluffy hairs.

A research team from the biology department at Augustana University in Sioux Falls, South Dakota asked if I would participate in their Milkweed research. Of course, I agreed. The green seedpod of this plant in the south hayfield was one of two I sent once it was dried (but not open).

Once the hay was cut, the Asclepias syriaca wasted no time growing again. Unfortunately, they were not able to flower…

One of these seedpods from a plant growing in the fence along the front pasture was also sent to the research team.

Besides milkweeds being host plants for Monarch Butterfly caterpillars, they are beneficial to many other insects as well. Most of the time when I am photographing, there are multiple species on the leaves. They are either feeding or being fed on…

There are more photos from 2022 at the bottom of the page.

I live on a small farm in Windsor, Missouri where I enjoy gardening, collecting plants, and identifying wildflowers. The farm is in Pettis County but Henry County is across the street, and Benton and Johnson aren’t far away. I have grown over 500 different plants and identified over 250 species of wildflowers (most have pages listed on the right side of the page). I am not an expert, botanist, or horticulturalist. I just like growing, photographing, and writing about my experience. I rely on several websites for ID and a few horticulturalists I contact if I cannot figure them out. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.

I hope you found this page useful and be sure to check the links below for more information. They were written by experts and provide much more information. Some sites may not be up-to-date but they are always a work in progress. If you can, I would appreciate it if you would click on the “Like” below and leave a comment. It helps us bloggers stay motivated. You can also send an email to me at thebelmontrooster@yahoo.com. I would enjoy hearing from you especially if you notice something is a bit whacky.

FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
INTERNATIONAL PLANT NAMES INDEX (GENUS/SPECIES)
TROPICOS (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
WIKIPEDIA (GENUS/SPECIES)
USDA PLANTS DATABASE
USDA PLANT GUIDE
DAVE’S GARDEN
MISSOURI PLANTS
MISSOURI BOTANICAL GARDEN
MSU-MIDWEST WEEDS AND WILDFLOWERS
MISSOURI DEPARTMENT OF CONSERVATION
iNATURALIST
WILDFLOWERSEARCH
ILLINOIS WILDFLOWERS
MINNESOTA WILDFLOWERS
KANSAS WILDFLOWERS AND GRASSES
NORTH CAROLINA STATE UNIVERSITY
PFAF(PLANTS FOR A FUTURE)
GO BOTANY
LADY BIRD JOHNSON WILDFLOWER CENTER
FLORA FINDER
FRIENDS OF THE WILDFLOWER GARDEN
GARDENIA
U.S. FOREST SERVICE
MONARCH WATCH

NOTE: The data (figures, maps, accepted names, etc.) may not match on these websites. It depends on when and how they make updates and when their sources make updates. Some websites have hundreds and even many thousands of species to keep up with. Accepted scientific names change periodically and it can be hard to keep with as well. Some of the links may use a name that is a synonym on other sites. In my opinion, Plants of the World Online by Kew is the most reliable and up-to-date plant database and they make updates on a regular basis. I make updates “at least” once a year and when I write new pages or add new photos but I do get behind. We are all a work in progress. 🙂

PHOTOS FROM 2022…

The photos from June 12 in 2022 were taken next to the road along the south side of Farrington Park in Windsor, MO.

 

 

 

Photos from June 26 in 2022 were taken on the farm where I live.