Asclepias

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"Milkweed" redirects here. For other uses, see Milkweed (disambiguation).
Asclepias
Asclepiascommon.JPG
Asclepias syriaca showing flowers and latex.
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Gentianales
Family: Apocynaceae
Subfamily: Asclepiadoideae
Tribe: Asclepiadeae
Subtribe: Asclepiadinae
Genus: Asclepias
L.[1]
Type species
Asclepias syriaca
L.
Species

See text.

Synonyms[1]
  • Acerates Elliott
  • Anantherix Nutt.
  • Asclepiodella Small
  • Asclepiodora A.Gray
  • Biventraria Small
  • Oxypteryx Greene
  • Podostemma Greene
  • Podostigma Elliott (probable)
  • Schizonotus A.Gray
  • Solanoa Greene
  • Trachycalymma (K.Schum.) Bullock (possible)
Asclepias syriaca seed pods, Baldwinsville, New York
Milkweed sprout, a few days after sowing
Chemical structure of oleandrin, one of the cardiac glycosides

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

Milkweed is named for its milky sap, which consists of a latex containing alkaloids and several other complex compounds including cardenolides.[2] Some species are known to be toxic.

Carl 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. 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.

Asclepias species produce their seeds in follicles. The seeds, which are arranged in overlapping rows, have white, silky, filament-like hairs known as pappus, silk, or floss. The follicles ripen and split open, and the seeds, each carried by several dried pappi, are blown by the wind. They have many different flower colorations.

Ecology[edit]

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.

Milkweeds use three primary defenses to limit damage caused by caterpillars: hairs on the leaves, cardenolide toxins, and latex fluids. Data from a DNA study indicate that more recently evolved milkweed species use these preventative strategies less but grow faster than older species, potentially regrowing faster than caterpillars can consume them.[3]

Uses[edit]

The milkweed filaments from the follicles are hollow and coated with wax, and have good insulation qualities. During World War II, over 5,000 t (5,500 short tons) of milkweed floss were collected in the United States as a substitute for kapok.[4][5] As of 2007, milkweed is grown commercially as a hypoallergenic filling for pillows.[6] A study of the insulative properties of various materials found that milkweed was outperformed by other materials in insulation, loft, and lumpiness, but scored well on various metrics when mixed with down feathers.[7]

Seeds

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 can be used for cordage.

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

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

Milkweed also contains cardiac glycoside poisons that inhibit animal cells from maintaining a proper K+, Ca+ concentration gradient.[citation needed] 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 and may cause death when animals consume 10% of their body weight in any part of the plant.[citation needed] Milkweed also causes mild dermatitis in some who come in contact with it.

The leaves of Asclepias species, and of some species formerly classified as Asclepias such as Gomphocarpus physocarpus, are the only food source for monarch butterfly larvae and other milkweed butterflies. These plants are therefore often used in butterfly gardening.[citation needed]

In a garden, milkweed flowers will produce a strong and beautiful fragrance that will be as powerful as in any other flower.[citation needed]

Species[edit]

Some Asclepias species:

Asclepias-albicans.jpg Asclepias albicans Whitestem milkweed, native to the mojave and sonoran deserts
Asclepias amplexicaulis Blue Ridge.jpg Asclepias amplexicaulis Blunt-leaved milkweed, native to central and eastern United States
Asclepias asperula - Antelope Horns.jpg Asclepias asperula Antelope horns, native to American southwest and northern Mexico
Asclepias sp. flowers (Marshal Hedin).jpg Asclepias californica California milkweed, native to central and southern California
Asclepias cordifolia.JPG Asclepias cordifolia Heart-leaf milkweed, native to the Sierra Nevada and Cascade Range up to 2000 m.
Asclepiascryptoceras.jpg Asclepias cryptoceras Pallid milkweed, native to the western United States.
Asclepias curassavica (Mexican Butterfly Weed) W IMG 1570.jpg Asclepias curassavica Scarlet milkweed, tropical milkweed, bloodflower, bastard ipecacuanha, native to the American tropics, introduced to other continents
Asclepiaseriocarpa.jpg Asclepias eriocarpa Woollypod milkweed, native to California, Baja California, and Nevada
Asclepias erosa 5.jpg Asclepias erosa Desert milkweed, native to California, Arizona, and Baja California
Asclepias exaltata (2985661678).jpg Asclepias exaltata Poke milkweed, native to eastern North America
Asclepias fascicularis flowers 2003-06-05.jpg Asclepias fascicularis Narrow-leaf milkweed, native to Western United States
Asclepias humistrata.jpg Asclepias humistrata Sandhill milkweed, native to southeastern United States
Swamp Milkweed Asclepias incarnata Flowers Closeup 2800px.jpg Asclepias incarnata Swamp milkweed, native to wetlands of North America
Asclepias lanceolata plant.jpg Asclepias lanceolata Lanceolate milkweed (Cedar Hill milkweed), native to coastal plain of eastern United States from Texas to New Jersey
Asclepias linaria.jpg Asclepias linaria Pine needle milkweed, native to Mojave and Sonoran deserts
Asclepias linearis Slim milkweed
Asclepias longifolia.JPG Asclepias longifolia Longleaf milkweed
Asclepiasmeadii.jpg Asclepias meadii Mead's milkweed, native to midwestern United States
Asclepias nyctaginifolia.jpg Asclepias nyctaginifolia Mojave milkweed, native to the American southwest
Asclepias obovata Pineland milkweed
Purple Milkweed Asclepias purpurascens Head.jpg Asclepias purpurascens Purple milkweed, native to eastern, southern, and midwestern United States
Asclepias quadrifolia 001.jpg Asclepias quadrifolia Four-leaved milkweed, native to eastern United States and Canada
BB-3386 Asclepias rubra.png Asclepias rubra Red milkweed
Asclepias solanoana.jpeg Asclepias solanoana Serpentine milkweed, native to northern California
R27182818 milkweed img 0312.jpg Asclepias speciosa Showy milkweed, native to western United States and Canada
Asclepias subulata flowers 2.jpg Asclepias subulata Rush milkweed, leafless milkweed, native to southwestern North America
Asclepias subverticillata.jpg Asclepias subverticillata Horsetail milkweed[8]
Asclepias sullivantii.jpg Asclepias sullivantii Sullivant's milkweed
Common milkweed-tracy.jpg Asclepias syriaca Common milkweed
Butterfly Weed Asclepias tuberosa Umbel.jpg Asclepias tuberosa Butterfly weed, pleurisy root
Asclepias uncialis lg.jpg Asclepias uncialis Wheel milkweed
Asclepias variegata.jpg Asclepias variegata White milkweed
Asclepias verticillata (3197723098).jpg Asclepias verticillata Whorled milkweed
Asclepias vestita Woolly milkweed
Asclepiasviridiflora.jpg Asclepias viridiflora
Asclepias viridis 1.jpg Asclepias viridis Green milkweed
Asclepias welshii 1.jpg Asclepias welshii Welsh's milkweed

Formerly placed here[edit]

Some species formerly classified under the Asclepias genus include:

References[edit]

  1. ^ a b "Taxon: Asclepias L.". Germplasm Resources Information Network. United States Department of Agriculture. 2003-03-13. Retrieved 2013-02-05. 
  2. ^ Singh, B. and Rastogi, R.P. (1970). Cardenolides-glycosides and genins. Phytochemistry 9: 315-331.
  3. ^ Ramanujan, Krishna (Winter 2008). "Discoveries: Milkweed evolves to shrug off predation". Northern Woodlands (Center for Northern Woodlands Education) 15 (4): 56. 
  4. ^ Hauswirth, Katherine (2008-10-26). "The Heroic Milkweed". The Christian Science Monitor. Retrieved 2014-02-14. 
  5. ^ Wykes, Gerald (2014-02-04). "A Weed Goes to War, and Michigan Provides the Ammunition". MLive Media Group. Michigan History Magazine. Retrieved 2014-02-14. 
  6. ^ Evangelista, R.L. (2007). "Milkweed seed wing removal to improve oil extraction". Industrial Crops and Products 25 (2): 210–217. doi:10.1016/j.indcrop.2006.10.002. 
  7. ^ McCullough, Elizabeth A. (April 1991). "Evaluation of Milkweed Floss as an Insulative Fill Material". Textile Research Journal 61 (4): 203–210. doi:10.1177/004051759106100403. 
  8. ^ Asclepias subverticillata (A. Gray) Vail, USDA PLANTS
  9. ^ "GRIN Species Records of Asclepias". Germplasm Resources Information Network. United States Department of Agriculture. Retrieved 2011-02-22. 
  • 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[edit]