Natural History

Butterfly Milkweed

Classification
Kingdom – Plantae
Division – Magnoliophyta
Class – Magnoliopsida
Order – Gentianales
Family – Asclepiadaceae (milkweed family)
Genus species – Asclepias tuberose L.

Etymology
Asclepias is named for the Greek god of healing, Asklepios; tuberosa,from Latin, for the fact that the rhizomes of some plants have tubers

Leaves
Numerous leaves on stems
Leaves have short stalks (petioles). 
Mostly alternate but sometimes opposite
Leaves are oblong-lanceolate to linear-lanceolate in shape
2 to 4 inches long, 1 inch wide
Long hairs, especially on underside of veins
Edges of leaves are smooth and often curl downward
Green above, lighter green below

Inflorescence
One to several terminal inflorescences, each on a stem up to 1 inch long
Each inflorescence has 6 to 25 flowers
The flowers are arrayed in an umbel, with all stems coming out of one stalk, like an upside-down umbrella.
Inflorescence is a group of convex or flat-topped flowers.
The central flower opens first.

Flower
Bright orange, yellow or reddish petals.
Five petals, 8-9 mm long, 2.2 mm broad.
Each petal within a flower is a similar color.
Flowers from May to September

Sketch of butterfly milkweed. Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 3: 25. Courtesy of Kentucky Native Plant Society.

Fruit
Pod is nearly erect, with fine hairs.
Pod is 3 to 6 inches long.
Pod contains “tufted” seeds with white hairs at their tips.

Stems
Stem is up to 60 cm tall
Stem is covered with coarse stiff hairs.

Roots
Deep taproot.  Doesn’t transplant easily.

Habitat
Occurs in prairies, open woodlands, roadsides, railroads, gardens.
Requires full sun.

Did you know...

The flowers are very attractive to butterflies.  The flowers produce a lot of nectar which is eaten by caterpillars or monarch butterflies.  The butterflies store the poisons (cardiac glycosides) produced by the plant and hence become toxic to predators. 

Leaves, fruits, and stems are toxic.  Primary poisons are desglucosyrioside and syrioside.  Death is not likely unless large quantites are consumed.  Symptoms of poisoning:  vomiting, diarrhea, incoordination, tremors, heart problems, breathing difficulties, death.

Milkweed is unpalatable and will not be eaten by livestock unless it is mixed in with their forage.  There is no antidote if an animal consumes milkweed.  If you know your animal has consumed a lot of the plant, you may ask a veterinarian to empty its stomach contents and provide care for the animal.  If the animal nibbles a little bit of the plant, then this shouldn’t be a problem.

American Indians used the roots to treat respiratory problems, as did the pioneers, hence the common name “pleurisy root”. 

Most milkweeds have a thick sticky milky sap that oozes out of cut or torn leaves, stems, or pods.  Butterfly milkweed, however, does not have this milky white juice.

Sources
http://www.missouriplants.com/Redalt/Asclepias_tuberosa_page.html
http://wisplants.uwsp.edu/scripts/detail.asp?SpCode=ASCTUBsINT
http://www.ansci.cornell.edu/plants/comlist.html
http://www.lib.ksu.edu/wildflower/butterfly.html
http://www.vet.purdue.edu/depts/addl/toxic/plant26.htm
http://www.plants.usda.gov/java/profile?symbol=ASTU

Leaves of butterfly milkweed

Stem of butterfly milkweed