Asclepias syriaca


 species synonym(s)  Asclepias intermedia, Asclepias kansana, and Asclepias cornuti
 common name(s)  Common milkweed
 native to  widespread, but mostly eastern North America
 zone hardiness  unknown, but 3 is probably the lowest
 life cycle
 perennial
 height  usually 2 - 5 feet, see digital images (below) for 10+ tall stem (rare)
 width  1 foot (per stem)
 light requirements  full sun, but will survive on partial sun exposure
 soil requirements  most soil types, including heavy clay, tolerates slow draining soils
 water requirements  adequate moisture
 reproduction  by seed, and underground by stolons (usually in two or three directions)
 germination  seed requires cold moist period
 difficulty  easy, mature plants are known to skip a growing season by staying dormant
 relationships  nectar source for insects and hummingbirds, host plant for all milkweed dependent insects, flower umbels have a sweet fragrance


Experience | Opinion | Impression
Common milkweed is easily mistaken with Hemp / Indian dogbane (Apocynum cannabinum), especially the young shoots, except that Common milkweed has noticeable fuzzy hairs on the underside of its leaves; both species share the same habitat, and grow in nearly identical manners.

Due to the manner in which this species spreads underground, it is not unreasonable to imagine that if it were possible to dig up a stand of common milkweed that you would find the stems are all interconnected (are all one plant). < A picture of a single milkweed stem and its stolon dug up is pictured here. > This is true of all plants (that I know of) that spread by stolons. This species is considered aggressive in a garden setting, and probably best grown in a sunken container but then requires daily watering during the growing season. This species has been reported to grow downwards as long as there is pliable soil, so attempting to use a bottomless container to control its spread will only be successful until the plant climbs underneath the container. I used to use a container (above ground) with multiple holes that I drilled with the smallest drill bit I could find, until a cold winter killed it off. I now mow around specimens that had already been in the yard before I purchased the property, I know it is spreading, but have adjusted my gardening strategy.

I found this reference, with nice photos, of a naturally occurring hybrid between (Asclepias syriaca X Asclepias exaltata), in Watauga county, North Carolina.

There are differences between regional populations of the species. Western Illinois University reports on commercial common milkweed production studies. 2001 Direct Seeding Trials produced the following observations, "Plot establishment (2001): seed was collected from locations in Wyoming, Nebraska, and Illinois", and "Second year results (2002): with the Illinois population showing the most vigor as evidenced by increased height, resistance to fungal diseases, and number of blooms and pods ... with the Illinois population of common milkweed being the last to mature." Also, "Third year results (2003): The Illinois population surpassed the non-native populations in disease and insect resistance as well as plant height and strength." They mention using "insecticides and fungicides", so I wonder if the entire study population were left to fend for themselves, would they show any noticeable growth difference. Continuing, "Third year results (2003): 2003 data continued to illustrate that higher concentrations of plants produce fewer, smaller follicles" and "evidence that coal treatments have no effect on follicle and stalk production." Also, "Topping Experiments: Additional plots, planted at 15 inch inter-row spacing, were kept pruned back to an 18 inch height to evaluate the effects of first year topping on second year follicle production, which results showed no influence." There is a mention of Nitrogen Evaluations, but only folicle production results, and no declaration of whether it was useful. "Results of the planting density trials examining 3 inter-row spacings show that higher plant concentrations have an adverse effect on follicle production."

A publication from a 2007 study is here. Also, a USDA article titled "Milkweed: From Floss to Fun in the Sun" about research done on the seed oil.


digital images
Common milkweed stem emerging in the spring, notice the significant fuzziness on the back of the leaves.
This photo is of a young shoot in the spring time. This species is often mistaken with (Apocynum cannabinum) in the early part of the growing season. This species can be distinguished by the fuzzy underside of the leaves, (Apocynum cannabinum) is smooth on the underside of its' leaves.


These are Common milkweed stems growing natively in my backyard. This area is partly shaded and as a result it does not grow out of control.

These are Common milkweed plants that I have been growing in an above ground container. These remain fairly short, about 3 feet tall, and as you can see they do flower and eventually set seed pods. In a container the spread underground is controlled, but often requires two waterings on hot days. To the right of this container are two smaller containers that have (Apocynum cannabinum) growing in them. The plants of both species are mature and easy to distinguish from each other.

Notice there are three milkweed pods in this photo; one of the smaller is green and maturing, and the other smaller is brownish looks like it maybe an aborted pod.
Here is a close up photo of my containerized Common milkweed having set seed. The larger pod is near full maturity with younger pods in view (lower right of the large pod).

I'm standing by the tallest Common milkweed stem I've seen to date. It was approximately 10 feet tall.
This is of me standing next to the tallest Common milkweed stem I have seen so far. This was photographed at a University botanical garden in North Carolina, and you can see there is some competition. The soil looks pliable and healthy and probably has consistent moisture. There were other milkweed stems in the planting, but this was the tallest. These plants were in an area that received little breeze.

On this common milkweed stem, you can see (Aphis nerii) on the lead growth, and ants attending to them.

The specimen on the back slope, different umbels at different stages of development, the most mature umbel getting ready to flower.

A umbel that is mostly flowering, and some of the flowers not yet open.


pertinent hyperlinks
USDA PLANTS Profile
A Close-up View of the Unusual Wildflower "Common Milkweed"
Missouri Plants
Illinois Wildflowers