common milkweed

(Asclepias syriaca)

               
Conservation Status

IUCN Red List

not yet assessed

common milkweed

NatureServe

N5 - Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

UPL - Obligate upland

Midwest

FACU - Facultative upland

Northcentral & Northeast

UPL - Obligate upland

Nativity

Native

Occurrence

Common and widespread

Habitat

Dry to wet. Meadows, fields, prairies, roadsides. Full to partial sun.

Photo by Bill Reynolds
Flowering

June to August

 
Flower Color

Pink to reddish-purple

 
Height

36 to 72

 

Identification

This is an erect perennial forb. A single stem rises from a long, creeping rhizome. It often forms colonies. The leaves and stems contain a milky juice.

The stems are erect and unbranched. They are covered with short, matted or tangled, soft, woolly hairs.

The leaves are opposite, thick, untoothed, 2½ to 8 long, 2¼ to 4 wide, and egg-shaped to elliptic or oblong. They are rounded at the base and taper to a point at the tip. They are attached to the stem on leaf stalks that are from less than ¼ to over ½ long. The upper surface is softly hairy, the lower surface finely woolly.

The inflorescence is usually several dense, drooping, umbrella-shaped clusters (umbels) rising from the upper leaf axils. The clusters are 3 to 4 in diameter and erect on a hairy, 2 long stalk. They typically have 20 to 130 flowers.

The structure of the typical milkweed flower is unique and instantly recognizable. There are 5 petals bent backward at the base and hanging downward. Subtending the petals are 5 much shorter, light green, lance-shaped sepals. There are 5 stamens. Formed from the filament of each stamen is a petal-like appendage. The appendage consists of a tubular hood surrounding an awl-shaped horn in the center of the hood. The stamens and the stigma are fused together into a crown-like structure (gynostegium). Each stigma has a long slit designed to catch the legs of a pollinating insect. A small, dark, sticky gland above this slit is attached to pollen sacs from adjacent anthers. These glands are designed to break off as an insect pulls its leg free of the slit, and remain attached to the insects leg. The flowers are pollinated by larger insects strong enough to lift off with the pollen sacs attached. Smaller insects are caught in a death trap or leave behind their detached legs.

The flowers of this plant are shaped like the typical milkweed flower. They are to tall and ¼ wide. The petals are pink to reddish-purple. They bend backward at the base, hang downward, then curl upward near the tip. They are separated from the hoods by a short but distinct column. The horns are shorter than the hoods. They project from the hoods and are curved inwards. The flowers are highly fragrant, the scent noticeable from yards distant.

The fruit is a fat, spindle-shaped pod. It is 3 to 4½ long and ¾ to 1½ thick. It is densely warty. It is held erect on a downward-pointing stalk. It opens on one side exposing the seeds to spreading by the wind. The seeds have a tuft of white, silky hairs at the tip.

 
Similar
Species

Clasping milkweed (Asclepias amplexicaulis) stems are hairless and glaucous. The leaves are rounded, not pointed, at the tip. They clasp the stem at the base, They are hairless and glossy on the upper surface, and are glaucous on the under surface. The leaf margins are strongly wavy. There is a single umbel appearing on a long stalk at the top of the stem. The umbel is erect and has 18 to 60 flowers. The petals are green tinged with red or purple. The horns are much longer than the hoods. The fruits are long, thin, and pointed and are not covered with warts.

Purple milkweed (Asclepias purpurascens) stems are unbranched and are covered with short, fine, soft hairs. The umbels are erect, appear near the top of the stem, and have up to 50 flowers.

Sullivant’s milkweed (Asclepias sullivantii) is a much shorter plant, 1 to 3 tall at maturity. The leaves and stems are hairless. The leaves are acute-tipped, ascending, with a reddish central vein. The umbels are looser, on a hairless stalk, and have 15 to 40 flowers. The flowers are larger. The fruit is narrower and smooth or slightly warty.

Swamp milkweed (Asclepias incarnata var. incarnata) stems are usually branched above the middle, and are hairless except for a vertical line of hairs on each side between the leaf nodes on the upper half. The umbels have 20 to 30 flowers. The horns are much taller than the hoods. The fruits are narrow, not fat, and are smooth, not covered with warts. It is usually found in wet areas.


Distribution Distribution Map   Sources: 2, 3, 4, 5, 7, 28.

Comments

Poisonous
This and other milkweeds contain cardiac glycosides and may be poisonous to both humans and livestock.


Taxonomy

Family:

Apocynaceae (dogbane)

 

Subfamily:

Asclepiadoideae

 

Tribe:

Asclepiadeae

 

Subtribe:

Asclepiadinae

 
Synonyms

Asclepias apocinum

Asclepias capitellata

Asclepias cornuti

Asclepias elliptica

Asclepias fragrans

Asclepias grandifolia

Asclepias intermedia

 

Asclepias kansana

Asclepias pubescens

Asclepias pubigera

Asclepias serica

Asclepias syriaca f. inermis

Asclepias syriaca f. leucantha

Asclepias syriaca var. kansana

 
Common
Names

broadleaf milkweed

common milkweed

cotton weed

silkweed

Silky swallowwort

Virginia silk


 

 

 

 

 

 

 

 

 

Glossary

axil

The upper angle where the leaf stalk meets the stem.

 

glaucous

Pale green or bluish gray due to a whitish, powdery or waxy film, as on a plum or a grape.

 

gynostegium

A crown-like structure of plants of the genus Asclepias formed by the fusion of the anthers with the stigmas.

 

linear

Long, straight, and narrow, with more or less parallel sides, like a blade of grass.

 

rhizome

A horizontal, usually underground stem. It serves as a reproductive structure, producing roots below and shoots above at the nodes.

 

umbel

A flat-topped or convex, umbrella-shaped cluster of flowers or buds arising from more or less a single point.

       

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Bill Reynolds


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MinnesotaSeasons.com Photos

   

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  Asclepias syriaca
Butler Herbarium
 
  Asclepias syriaca  
     
  Common Milkweed
Andree Reno Sanborn
 
  Common Milkweed  
 
About

Asclepias syriaca

 
     
  Common Milkweed (Asclepias syriaca)
Bill Keim
 
  Common Milkweed (Asclepias syriaca)  
     
  Asclepias syriaca (Common Milkweed)
Allen Chartier
 
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Joshua Mayer
 
  A. syriaca  
 
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Common Milkweed

 
     

 

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Other Videos

 
  Minnesota Native Plant - Common Milkweed (Asclepias Syriaca)
MNNativePlants
 
   
 
About

Published on Jun 30, 2013

The native plant today is the Common Milkweed (Asclepias Syriaca). Common throughout all of Minnesota and the host plant for the Monarch butterfly.

 
     
  Common Milkweed (Asclepias syriaca)
wvoutdoorman
 
   
 
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Published on Aug 24, 2012

Common Milkweed (Asclepias syriaca)

 
     
  Milkweed Patch
MyButterflyLadyYT
 
   
 
About

Published on Sep 6, 2013

This milkweed patch has hundreds of butterflies nectaring on the Common Milkweed (Asclepias syriaca) blooms. Taken just south of Raleigh, North Carolina, on September 5, 2013.

 
     
  Honeybees forage on Common Milkweed
Robert Klips
 
   
 
About

Uploaded on Jun 27, 2011

Honeybees forage in common milkweed (Asclepias syriaca) as Killdeer Plains Wildlife Area in Wyandot County, Ohio, USA. A bobolink sings in the background.

 
     
  Common Milkweed (Asclepias syriaca), Close-up Seeds
Carl Barrentine
 
   
 
About

Published on Sep 29, 2012

Photographed at the Turtle River State Park, North Dakota (29 September 2012).

 
     

 

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Bill Reynolds
7/29/2003

 

 

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