swamp milkweed

(Asclepias incarnata ssp. incarnata)

               
Conservation Status

IUCN Red List

not yet assessed

swamp milkweed

NatureServe

N5 - Secure

SNR - Unranked

Minnesota

not listed

Wetland
Indicator
Status

Great Plains

FACW - Facultative wetland

Midwest

OBL - Obligate wetland

Northcentral & Northeast

OBL - Obligate wetland

Nativity

Native

 
Occurrence

Common

 
Habitat

Wet to moist. Open swamps, marshes, streambanks, ditches, wet prairies, wet fields, meadows. Full sun.

 
Flowering

June to August

     
Flower Color

Pink or red

     
Height

2 to 5

     

Identification

This is an erect, perennial forb. One to several stems rise from a short, fibrous rhizome. It often grows in clumps. The leaves and stems contain a milky juice.

The stems are erect and usually repeatedly branched above the middle. They are usually hairless except for a vertical line of hairs on each side between the leaf nodes on the upper half.

The leaves are opposite, untoothed, 4 to 7 long, 1 to 2 wide, and lance-shaped or oblong. They gradually taper to a sharp point. They are attached to the stem on short leaf stalks. The lower surface is hairless.

The inflorescence is usually several large, dense, umbrella-shaped clusters (umbels) rising from the upper leaf axils and at the end of the stem. The clusters are 3 to 4 in diameter and erect on a hairy, 2 long stalk. They typically have 20 to 30 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 and are fragrant. They are tall and ¼ wide. The petals are pink to red. They bend backward at the base, hang downward, then curl upward near the tip. They are separated from the hoods by a distinct column. The horns are much taller than the hoods. They project from the hoods and are curved inwards.

The fruit is a narrow, spindle-shaped pod. It is 3 to 5 long and hairless. It is held erect on an erect stalk. It opens on one side exposing the seeds to spreading by the wind. The seeds have a tuft of silvery-white, silky hairs at the tip.

 
Similar
Species

Common milkweed (Asclepias syriaca)stems are unbranched and hairy. The upper surface of the leaves are softly hairy. The umbels have 20 to 130 flowers. The horns are shorter than the hoods. The fruits are fat and are covered with warts.

Purple milkweed (Asclepias purpurascens) stems are unbranched and are covered with short, fine, soft hairs. The leaves are wider, elliptical or oblong, and downy on the underside. The umbels have up to 50 flowers. The horns are much shorter than the hoods.


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

Comments

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

Milkweeds are the only plants that Monarchs lay their eggs on. The eggs are laid on the underside of healthy young leaves.


Taxonomy

Family:

Apocynaceae (dogbane)

 

Subfamily:

Asclepiadoideae

 

Tribe:

Asclepiadeae

 

Subtribe:

Asclepiadinae

 
Synonyms

Asclepias incarnata var. incarnata

 
Common
Names

marsh milkweed

rose milkweed

swamp milkweed


 

 

 

 

 

 

 

 

 

 

Glossary

axil

The upper angle where the leaf stalk meets the stem.

 

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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MinnesotaSeasons.com Photos

   

Plant

  swamp milkweed   swamp milkweed
       
  swamp milkweed    
       

Buds

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Inflorescence

  swamp milkweed   swamp milkweed
       

Flower

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  swamp milkweed    
       

Gynostegium

  swamp milkweed    
       

Leaves

  swamp milkweed   swamp milkweed
       

Infructescence

  swamp milkweed   swamp milkweed
       
  swamp milkweed   swamp milkweed
       

Fruit

  swamp milkweed   swamp milkweed
       
       

 

Camera

     

Slideshows

   
  Swamp Milkweed (Asclepias incarnata)
Andree Reno Sanborn
 
  Swamp Milkweed (Asclepias incarnata)  
     
  Swamp Milkweed (Asclepias incarnata)
Bill Keim
 
  Swamp Milkweed (Asclepias incarnata)  
     
  Asclepias incarnata SWAMP MILKWEED
Frank Mayfield
 
  Asclepias incarnata SWAMP MILKWEED  
     
  A. incarnata
Joshua Mayer
 
  A. incarnata  
 
About

Swamp Milkweed

 
     

 

slideshow

     

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Other Videos

 
  Minnesota Native Plant - Swamp Milkweed (Asclepias Incarnata)
MNNativePlants
 
   
 
About

Published on Jul 15, 2013

Swamp Milkweed is the focus of this Minnesota Native Plant video. Common to swamps, streams and ponds around Minnesota, it's a beautiful plant for the native garden.

 
     
  Swamp Milkweed - Asclepias incarnata blooming at Ion Exchange
Ionxchange
 
   
 
About

Uploaded on Aug 1, 2011

Earthyman views Swamp Milkweed (Asclepias incarnata) in full bloom at Ion Exchange in Northeast Iowa. http://www.ionxchange.com

 
     
  Swamp Milkweed
Chicagoland Gardening
 
   
 
About

Uploaded on Aug 7, 2008

Chicagoland Gardening Magazine editor Carolyn Ulrich discusses swamp milkweed, a native prairie plant.

 
     
  MrILoveTheAnts
Swamp Milkweed
 
   
 
About

Uploaded on Jul 29, 2011

What I believe to be Asclepias incarnata, Swamp Milkweed, growing out in a wetland field. I've never seen this species grow as a single stem before.

 
     
  Monarch larva eating Swamp Milkweed
ii386
 
   
 
About

Uploaded on Feb 2, 2011

 
     

 

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