clasping milkweed

(Asclepias amplexicaulis)

Conservation Status
clasping milkweed
Photo by Nancy Falkum
  IUCN Red List

not listed

     
  NatureServe

N5 - Secure

S3 - Vulnerable

     
  Minnesota

Threatened

     
           
           
           
           
           
           
 
Description
 
 

Clasping milkweed is an erect perennial forb. It occurs in the United States from New Hampshire to Minnesota south to Florida and eastern Texas. It is rare in Minnesota, where it is found in the driftless area in the southeast, and on just a single site in Dakota County.

Clasping milkweed rises on a single stem from a deep rhizome. The leaves and stems contain a white milky latex.

The stems are erect or sometimes recline on the ground with the tip ascending. They are stout, unbranched, hairless, and covered with a whitish, waxy coating (glaucous).

There are 2 to 5 pairs of opposite leaves. The leaves are thick, 2¾ to 6 long, ¾ to 3 wide, and oval or broadly oblong. They are attached to the stem without leaf stalks. They are rounded or heart-shaped at the base and rounded or broad-angled but not pointed at the tip. The base of the leaf partly surrounds (clasps) the stem, and frequently overlaps the base of the adjacent leaf. The upper surface is dark green and glaucous, the lower surface light green and glaucous. The margins are untoothed and strongly wavy.

The inflorescence is a single large, loose, umbrella-shaped cluster (umbel) rising on a very long stalk at the end of the stem. The stalk is 4 to 12 long with short, fine, soft hairs on just ½ or of their circumference, the rest being hairless. The clusters are 3 to 4 in diameter and erect. They typically have 18 to 60 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 ¾ tall on 1 to 1¾ long flower stems. The petals are green tinged with red or 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 hoods are pink. The horns are much longer than the hoods. They project from the hoods and curve inwards.

The fruit is a long, thin, pointed, spindle-shaped pod. It is 3½ to 6 long and to thick. It is mostly hairless and glaucous. It is held erect or horizontally on a drooping 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.

 
     
 

Height

 
 

1 to 3

 
     
 

Flower Color

 
 

Petals green tinged with red or purple, hoods pink.

 
     
 

Similar Species

 
 

Common milkweed (Asclepias syriaca) stems are covered with short, matted or tangled, soft, woolly hairs. The leaves taper to a point at the tip and do not clasp the stem at the base. They are softly hair on the upper surface, and are not glaucous on the under surface. The leaf margins are not wavy. There are several umbels appearing in the upper leaf axils. The umbels are drooping and have up to 130 flowers. The flowers are pale purple or pink. The horns are shorter than the hoods. The pods are fat and are covered with warts.

 
     
 
Habitat
 
 

Dry. Prairies, wood openings, open woods, roadsides, railroads. Full or partial sun.

 
     
 
Biology
 
 

Flowering

 
 

June to July

 
     
 

Pests and Diseases

 
 

 

 
     
 
Use
 
 

Faunal Associations

 
 

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

 
     
 

Toxicity

 
 

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

 
     
 
Distribution
 
 

Distribution Map

 

Sources

2, 3, 4, 5, 6, 7, 24, 28, 29, 30.

 
  3/24/2022      
         
 

Nativity

 
 

Native

 
         
 

Occurrence

 
 

Rare in Minnesota

 
         
 
Taxonomy
 
  Kingdom Plantae (green algae and land plants)  
  Subkingdom Viridiplantae (green plants)  
  Infrakingdom Streptophyta (land plants and green algae)  
  Superdivision Embryophyta (land plants)  
  Division Tracheophyta (vascular plants)  
  Subdivision Spermatophytina (seed plants)  
  Class Magnoliopsida (flowering plants)  
  Superorder Asteranae  
 

Order

Gentianales (gentians, dogbanes, madders, and allies)  
 

Family

Apocynaceae (dogbane)  
  Subfamily Asclepiadoideae (milkweeds)  
  Tribe Asclepiadeae  
  Subtribe Asclepiadinae  
 

Genus

Asclepias (milkweeds)  
       
 

Subordinate Taxa

 
 

 

 
       
 

Synonyms

 
 

Asclepias gladewitzii

Asclepias obtusifolia

Asclepias rotundifolia

 
       
 

Common Names

 
 

bluntleaf milkweed

blunt-leaf milkweed

blunt-leaved milkweed

clasping milkweed

sand weed

 

 

 

 

 

 

 

 

 

Glossary

Axil

The upper angle where the leaf stalk meets the stem.

 

Clasping

Describing a leaf that wholly or partly surrounds the stem but does not fuse at the base.

 

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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Nancy Falkum

 
 

Clasping milkweed Asclepias amplexicaulis at TNC Cox Unit

 
    clasping milkweed      
           
 

Landscape at TNC Cox Unit with Clasping milkweed Asclepias amplexicaulis at lower center

 
    Weaver Dunes Preserve      
           
 

At TNC Cox Unit with Clasping milkweed Asclepias amplexicaulis at lower center

 
    clasping milkweed      
           
 

Landscape TNC Cox Unit Clasping milkweed Asclepias amplexicaulis

 
    Weaver Dunes Preserve      
           
 

Clasping milkweed Asclepias amplexicaulis at TNC KWD Cox Unit

 
    clasping milkweed      
           
    Weaver Dunes Preserve      
           
    clasping milkweed   clasping milkweed  
           
 
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Slideshows
 
A. amplexicaulis
Joshua Mayer
  A. amplexicaulis  
 
About

Clasping Milkweed

 

 

slideshow

       
 
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Other Videos
 
  DSCN7073Clasping leaf milkweed SEED.AVI
Aubrey Shepherd
 
   
 
About

Uploaded on Jul 18, 2010

Pinnacle Foods Inc. wet prairie harbors both wetland and drier prairie plants including this blunt-leaf or clasping milkweed, aka Asclepias amplexicaulis, shown with seed pods open. Monarch butterflies' eggs must be on milkweed in order to grow into caterpillers and become adult monarchs. Several species of milkweed grow on World Peace Wetland Prairie and on Pinnacle wet prairie.

   

 

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  Nancy Falkum
6/17/2022

Location: Weaver Dunes Preserve, Cox Unit

   
  Nancy Falkum
6/16/2022

Location: Weaver Dunes Preserve, Cox Unit

 

clasping milkweed  
  Nancy Falkum
7/27/2020

Location: Wabasha County

 

clasping milkweed  
           
 
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