Saturday 15 June
Dwarf milkweed (Asclepias ovalifolia)

Dwarf milkweed fact file
- Description
- Biology
- Range
- Habitat
- Status
- Threats
- Conservation
- Find out more
- Glossary
- References
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Dwarf milkweed description
| Kingdom | Plantae |
| Phylum | Tracheophyta |
| Class | Magnoliopsida |
| Order | Gentianales |
| Family | Asclepiadaceae |
| Genus | Asclepias (1) |
The dwarf milkweed (Asclepias opvalifolia) is a rare plant found in the prairies of North America. It has an erect, unbranched central stem that is light green to brown and is lightly covered in short hairs. The oval-shaped leaves, which give this species its alternative common name of ‘oval-leaved milkweed’, are arranged in opposite pairs. The leaf blades are five to eight centimetres in length, have smooth margins and are green and hairless on the upper surface, but pale green and hairy on the lower surface (2) (3).
The central stem of the dwarf milkweed terminates in a dome-shaped umbel, which consists of 8 to 24 beautiful greenish-white flowers. Each flower is borne on a short stalk, and comprises a central column surrounded by inward-curving, white or cream petals (2) (3).
The seed pods of the dwarf milkweed stand erect at maturity and are pointed at both ends. The seeds bear a tuft of long, tan-coloured hairs (3).
TopDwarf milkweed biology
Flowering in this perennial plant occurs during a three week period between late spring and early summer (2) (5). The flowers of the dwarf milkweed are pollinated by bees, insects and butterflies (5). The flowers are hermaphroditic and once fertilised, are replaced by spindle-shaped seedpods (2) (5). At maturity, the seedpods split along one side, releasing the seeds, which are dispersed by the wind (2).
The milky sap, known as ‘latex’, produced by the giant milkweed is toxic when ingested by mammals and may cause nausea and vomiting (2).
TopDwarf milkweed range
The dwarf milkweed ranges from Canada, just north of the Great Lakes, south to Illinois, U.S., and westward through South Dakota and into the lower elevations of Wyoming (3).
TopDwarf milkweed habitat
The dwarf milkeed occurs in upland oak woodland and dry or hill prairies, where it grows on rich, sandy soils (2) (4).
TopDwarf milkweed status
The dwarf milkweed has yet to be classiifed by the IUCN Red List.
TopDwarf milkweed threats
While the full range of threats to the dwarf milkweed have not yet been fully assessed, it is considered rare in much of its range (2).
TopDwarf milkweed conservation
The dwarf milkweed is classified as ‘Endangered’ in Illinois and as ‘Threatened’ in Wisconsin (2) (4). A conservation priority for this species is the protection and restoration of its prairie habitat.
TopFind out more
Find out more about the dwarf milkweed:
-
Illinois Wildflowers:
http://www.illinoiswildflowers.info/prairie/plantx/oval_milkweed.htm
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Glossary
- Fertilisation
- The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
- Hermaphroditic
- Possessing both male and female sex organs.
- Perennial
- A plant that normally lives for more than two seasons. After an initial period, the plant produces flowers once a year.
- Pollinate
- To transfer pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.
- Prairie
- An extensive area of flat or rolling, predominantly treeless grassland, especially the large tract or plain of central North America.
- Umbel
- In plants, a usually umbrella-shaped flower cluster in which the individual flower stalks originate at roughly the same point.
References
-
ITIS (April, 2011)
http://www.itis.gov/ -
Illinois Wildflowers - Oval-leaved milkweed (July, 2011)
http://www.illinoiswildflowers.info/prairie/plantx/oval_milkweed.htm -
U.S. Geological Survey - Ovalleaf milkweed (July, 2011)
http://www.npwrc.usgs.gov/resource/plants/wildflwr/species/ascloval.htm -
Robert W. Freckmann Herbarium - Asclepias opvalifolia (July, 2011)
http://wisplants.uwsp.edu/scripts/detail.asp?SpCode=ASCOVA -
Plants for a Future - Asclepias opvalifolia (July, 2011)
http://www.pfaf.org/user/Plant.aspx?LatinName=Asclepias%20ovalifolia
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This species is found in Wisconsin's Northwoods and has been profiled with the support of a Wisconsin-based family who care deeply about the area. To learn more visit our eco-region pages.
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Image credit
© Carol Jacobs-Carre
Carol Jacobs-Carre
http://www.flickr.com/photos/carolannie/
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