Asclepias
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 Asclepias syriaca showing flowers and latex like sap. | ||||||||||||||||
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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, latex, 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 or tetrads, as is typical for most plants. The feet or mouthparts of flower visiting insects such as bees, wasps and butterflies, slip into one of the five slits in each flower formed by adjacent anthers. The bases of the pollinia then mechanically attach to the insect, pulling a pair of pollen sacs free when the pollinator flies off. Pollination is effected by the reverse procedure in which one of the pollinia becomes trapped within the anther slit.
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 albicans | Whitestem milkweed | |
| Asclepias amplexicaulis | Blunt-leaved milkweed | |
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Asclepias asperula | Antelope horns |
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Asclepias californica | California milkweed |
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Asclepias cordifolia | Heart-leaf milkweed |
| Asclepias cryptoceras | Pallid milkweed | |
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Asclepias curassavica | Scarlet milkweed, Tropical milkweed, Bloodroot, Bloodflower, Bastard Ipecacuanha |
| Asclepias eriocarpa | Woollypod milkweed | |
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Asclepias erosa | Desert milkweed |
| Asclepias exaltata | Poke milkweed | |
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Asclepias fascicularis | Narrow leaf milkweed |
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Gomphocarpus fruticosus | swan plant |
| Asclepias humistrata | Sandhill milkweed | |
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Asclepias incarnata | Swamp milkweed |
| Asclepias lanceolata | Lanceolate milkweed | |
| Asclepias linaria | Pine needle milkweed | |
| Asclepias linearis | Slim milkweed | |
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Asclepias nyctaginifolia | Mojave milkweed |
| Asclepias obovata | Pineland milkweed | |
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Asclepias physocarpa | Gomphocarpus physocarpus, commonly balloonplant, balloon cotton-bush, giant swan plant, testicle tree, bishop's balls or swan plant |
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Asclepias purpurascens | Purple milkweed |
| Asclepias quadrifolia | Four-leaved milkweed | |
| Asclepias rubra | Red milkweed | |
| Asclepias solanoana | Serpentine milkweed | |
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Asclepias speciosa | Showy milkweed |
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Asclepias subulata | Rush milkweed(Leafless milkweed) |
| Asclepias sullivantii | Sullivant's milkweed | |
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Asclepias syriaca | Common milkweed |
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Asclepias tuberosa | Butterfly weed, Pleurisy root |
| Asclepias variegata | White milkweed | |
| Asclepias verticillata | Whorled milkweed | |
| Asclepias vestita | Woolly milkweed | |
| Asclepias vincetoxicum |
Baldwinsville, New York
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.
Milkweed sap is also externally used as a natural remedy for Poison Ivy.
Being the sole food source of Monarch Butterfly larva, the plant is often used in Butterfly gardening.
See also
- List of beneficial weeds
- List of companion plants
References
- Everitt, J.H.; Lonard, R.L., Little, C.R. (2007). Weeds in South Texas and Northern Mexico. Lubbock: Texas Tech University Press. ISBN 0-89672-614-2
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
Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Asclepias". Image Credit.
