oval-leaf milkweed

(Asclepias ovalifolia)

               
Conservation Status

IUCN Red List

not yet assessed

oval-leaf milkweed

NatureServe

NNR - Unranked

SNR - Unranked

Minnesota

not listed

Nativity

Native

Occurrence

Uncommon

Habitat

Dry. Prairies. Sandy soil. Full or partial sun.

Flowering

June to July

Flower Color

Greenish-white or greenish-purple

Height

8 to 24


Identification

This is a 8 to 24 tall, erect, perennial forb. A single stem, occasionally two, rises from a slender rhizome. The leaves and stems are velvety and contain a milky juice.

The stems are erect, usually unbranched, and covered with silky hairs. It usually has 4 to 6 pairs of leaves.

The leaves are opposite, untoothed, 2 to 3 long, and lance-shaped to oblong. They are rounded at the base. They are attached to the stem on leaf stalks up to long and are held erect or spreading. The lower surface is covered with fine hairs.

The inflorescence is usually a single, loose, umbrella-shaped cluster (umbel) at the end of the stem. Sometimes, there are 1 or 2 additional clusters rising from the uppermost leaf axils. The clusters are 2 to 3 in diameter, and typically have 5 to 20 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 ½ tall, less than ¼ wide, and are attached by hairy stalks that are about 1 long. The petals are greenish-white or greenish-purple. They bend backward at the base, hang downward, then curl upward near the tip. They are attached directly below the hoods without a separating column. The horns are shorter than the hoods. They project from the hoods and are curved inwards.

The fruit is a narrow, spindle-shaped pod. It is 2 to 3 long and about wide. It is held erect or ascending on an erect stalk. It opens on one side exposing the seeds to spreading by the wind. The seeds have a tuft of hairs at the tip that are light brown and ¾ to 1 long.

 
Similar
Species

Green milkweed (Asclepias viridiflora) leaves are larger, 1½ to 5½ long and up to 2½ wide. The leaf margins are wavy. The inflorescence is a dense cluster of 20 to 80 flowers. The clusters are attached to the side of the stem near leaf nodes, not in the leaf axils and not at the end of the stem. The flowers are light green. The hoods have no horns. The fruit is much longer, 3 to 6 long.

Prairie milkweed (Asclepias hirtella) is a much taller plant, 16 to 40 tall at maturity. The leaves are much longer and narrower. They are 4 to 8 long, to ½ wide, lance-shaped to linear, and alternate. It has 2 to 10 dense flower clusters with 30 to 100 flowers in each cluster. The flowers are tinged with purple. The petals are separated from the hoods by a distinct column. The hoods have no horns. The fruits are longer, about 4¾ long. The tufts of hair attached to the seed tips are whitish.

Whorled milkweed (Asclepias verticillata) is a much shorter plant, 8 to 20 tall at maturity. The leaves are extremely narrow, linear, and in whorls of 3 to 6. The flower heads have only 10 to 20 flowers. The flowers have horns within their hoods.


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.

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

Conservation Status
Oval-leaf milkweed is listed as endangered in Illinois and Michigan, threatened in Wisconsin. It is not listed in Minnesota.


Taxonomy

Family:

Apocynaceae (dogbane)

 

Subfamily:

Asclepiadoideae

 

Tribe:

Asclepiadeae

 

Subtribe:

Asclepiadinae

 
Synonyms

Asclepias variegata var. minor

 
Common
Names

dwarf milkweed

milkweed

oval milkweed

ovalleaf milkweed

oval-leaf milkweed

oval-leaved 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.

       

Visitor Photos

   
Share your photo of this plant.

       
       
       
       

MinnesotaSeasons.com Photos

   

Plant

  dwarf milkweed   dwarf milkweed
       

Flowering Plant

  dwarf milkweed   dwarf milkweed
       

Inflorescence

  dwarf milkweed    
       

Leaves

  dwarf milkweed   dwarf milkweed
       
       

 

Camera

     

Slideshows

   
     
     
     

 

slideshow

     

Visitor Videos

   
Share your video of this plant.

     
     

Other Videos

 
     
     
     
     

 

Camcorder

Last Updated:

About Us | Privacy Policy | Contact Us | © 2018 MinnesotaSeasons.com. All rights reserved.