pleurisy root

Milkweeds
Asclepias tuberosa in bloom, showing pollinators
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Gentianales Family: Apocynaceae Subfamily: Asclepiadoideae Genus: Asclepias L.
Species
See text.

Asclepias L. (1753), the milkweeds, is a genus of herbaceous perennial, dicotyledonous plants that contains over 140 known species. It used to belong to the family Asclepiadaceae, but this is now classified as a subfamily Asclepiadoideae of the dogbane family Apocynaceae.

Milkweeds are an important nectar source for bees and other nectar seeking insects, and a larval food source for monarch butterflies and their relatives, as well as a variety of other herbivorous insects (including numerous beetles, moths, and true bugs) specialized to feed on the plants despite their chemical defenses. Milkweed is named for its milky juice, which contains alkaloids, caoutchouc, and several other complex compounds including cardenolides. Some species are known to be toxic.

Carolus Linnaeus named the genus after Asclepius, the Greek god of healing, because of the many folk-medicinal uses for the milkweed plants.

Pollination in this genus is accomplished in an unusual manner, as the pollen is grouped into complex structures called pollinia (or "pollen sacs"), rather than being individual grains, as is typical for plant pollen. The flower petals are smooth and rigid, and the feet of visiting insects (predominantly large wasps, such as spider wasps, which visit the plants for nectar) slip into notches in the flowers, where the sticky bases of the pollinia attach to the feet, pulling the pollen sacs free when the pollinator flies off. Bees, including honey bees only gather nectar from milkweed flowers, and are generally not effective pollinators despite the frequency of visitation.

Species in the Asclepias genus grow their seeds in pods. These seed pods contain soft filaments known as either silk or floss. The filaments are attached to individual seeds. When the seed pod ripens, the seeds are blown by the wind, each carried by several filaments.

Species

Some Asclepias species:

	Asclepias acida	Possibly used to create Soma.
	Asclepias amplexicaulis	Blunt-leaved milkweed
	Asclepias asperula	Antelope horns
	Asclepias curassavica	Scarlet milkweed, Bloodroot, Bastard Ipecacuanha
	Asclepias exaltata	Poke milkweed
	Asclepias fascicularis	Narrow leaf milkweed
	Asclepias humistrata	Sandhill milkweed
	Asclepias incarnata	Swamp milkweed
	Asclepias lanceolata	Lanceolate milkweed
	Asclepias linearis
	Asclepias obovata
	Asclepias physocarpa	Gomphocarpus physocarpus, commonly balloonplant, balloon cotton-bush or swan plant
	Asclepias purpurascens	Purple milkweed
	Asclepias quadrifolia	Four-leaved milkweed
	Asclepias rubra	Red milkweed
	Asclepias speciosa	Showy milkweed
	Asclepias subulata	Rush milkweed(Leafless milkweed)
	Asclepias sullivantii	Sullivant's milkweed
	Asclepias syriaca	Common milkweed
	Asclepias tuberosa	Butterfly weed, Pleurisy root
	Asclepias variegata	White milkweed
	Asclepias verticillata	Whorled milkweed
	Asclepias vincetoxicum

Asclepias syriaca seed pods
Baldwinsville, New York

Seeds.

Uses

These milkweed filaments or floss are coated with wax, and have good insulation qualities. Tests have shown them to be superior to down feathers for insulation. During World War II, over 11 million pounds (5000 t) of milkweed floss were collected in the United States as a substitute for kapok.

In the past, the high dextrose content of the nectar led to milkweed's use as a source of sweetener for Native Americans and voyageurs.

The bast fibers of some species were also used for cordage.

Milkweed latex contains about 1 to 2% caoutchouc, and was attempted as a natural source for rubber by both Germany and the United States during World War II. No record has been found of large-scale success.

Milkweed is a common folk remedy used for removing warts. Milkweed sap is applied directly to the wart several times daily until the wart falls off. Dandelion sap is often used in the same manner.

Milkweed is beneficial to nearby plants, repelling some pests, especially wireworms.

Milkweed also contains cardiac glycoside poisons which inhibit animal cells from maintaining a proper K⁺, Ca⁺ concentration gradient. As a result many natives of South America and Africa used arrows poisoned with these glycosides to fight and hunt more effectively. Milkweed is toxic. Fatality is possible when animal consumes 1/10 its body weight in any part of the plant. Milkweed also causes mild dermatitis in some who come in contact with it.

See also

• List of beneficial weeds
• List of companion plants

External links

• Medical research
• Milkweed test-cultivated for the insulation value of floss
• Milkweed in Handbook of Energy Crops
• Common milkweed production research at Western Illinois University
• UVSC Herbarium - Asclepias
• Milkweed Photo Gallery

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Apocynaceae

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