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''Asclepias syriaca'', commonly called common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed, is a species of flowering plant. It is native to southern Canada and much of the United States east of the Rocky Mountains, excluding the drier parts of the prairies. It is in the genus ''
Asclepias ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to human ...
'', the milkweeds. It grows in sandy soils as well as other kinds of soils in sunny areas.


Description

''A. syriaca'' is a clonal
perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...
forb A forb or phorb is an herbaceous flowering plant that is not a graminoid (grass, sedge, or rush). The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory. Typically these are dicots without woo ...
growing up to tall. Individual plants grow from rhizomes. All parts of common milkweed plants produce a white
latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosper ...
when cut. The simple leaves are opposite, sometimes whorled; broadly
ovate Ovate may refer to: * Ovate (egg-shaped) leaves, tepals, or other botanical parts *Ovate, a type of prehistoric stone hand axe A hand axe (or handaxe or Acheulean hand axe) is a prehistoric stone tool with two faces that is the longest-used ...
-
lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regula ...
. They grow to long and broad, usually with entire,
undulate Undulation may refer to: * Lateral undulation, the most primitive of vertebrate locomotor patterns * Undulation of the geoid, the separation between the geoid and the reference ellipsoid of the Earth * Undulation point, a point on a curve where th ...
margins and reddish main veins. They have very short petioles and velvety undersides. The highly fragrant,
nectariferous Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualist ...
flowers vary from white (rarely) through pinkish and purplish and occur in umbellate
cymes An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...
. Individual flowers are about in diameter, each with five horn-like hoods and five
pollinia A pollinium (plural pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of mi ...
. The seeds, each with long, white flossy hairs, occur in large follicles. Fruit production from
self-fertilization Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self-pollination, a reproductive mechanism employed by many flowering plants. However, species ...
is rare. In three study plots,
outcrossed Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity. Outcrossing can be a useful ...
flowers had an average of about 11% fruit set.


Ecology

More than 450 insect species feed on ''A. syriaca'', including flies, beetles, ants, bees, wasps, and butterflies; it is an important food source for
monarch butterfly The monarch butterfly or simply monarch (''Danaus plexippus'') is a milkweed butterfly ( subfamily Danainae) in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. ...
caterpillars (''
Danaus plexippus The monarch butterfly or simply monarch (''Danaus plexippus'') is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. It ...
''); other species that feed on the plant include red milkweed beetle ('' Tetraopes tetraophthalmus''), the milkweed tussock caterpillar (''
Euchaetes egle ''Euchaetes egle'', the milkweed tiger moth or milkweed tussock moth, is a moth in the family Erebidae and the tribe Arctiini, the tiger moths. The species was first described by Dru Drury in 1773. It is a common mid- through late summer feede ...
'') and ''
Oncopeltus fasciatus ''Oncopeltus fasciatus'', known as the large milkweed bug, is a medium-sized hemipteran (true bug) of the family Lygaeidae.Attisano, A. (2013) Oosorption and migratory strategy of the milkweed bug,''Oncopeltus fasciatus. Animal Behaviour 86(3):6 ...
'' and ''
Lygaeus kalmii ''Lygaeus kalmii'', known as the small milkweed bug or common milkweed bug, is a species of seed bug in the family Lygaeidae. It is found in Central and North America. Taxonomy ''Lygaeus kalmii'' was first formally named in 1874 by Swedish ent ...
''. Many kinds of insects visit ''A. syriaca'' flowers, and some kinds pollinate them, including ''
Apis mellifera The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for "bee", and ''mellifera'' is the Latin for "honey-bearing" or "honey carrying", ...
'', the Western honey bee, and native ''
Bombus A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gene ...
'' spp. (bumblebees). In the U.S. mid-Atlantic region, the introduced species ''A. mellifera'' was found to be the most "effective" pollinator, but this occurs more often among flowers of the same plant; since ''A. syriaca'' has a high level of self-incompatibility, it is less effective than Bombus'' spp. in the fertilization of flowers because ''Bombus'' spp. are more likely to visit unrelated individuals. Monarch butterfly
larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...
e consume only milkweeds, and monarch populations may decline when milkweeds are eliminated with
herbicides Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...
. The development and widely adopted cultivation of herbicide-resistant staple crops such as
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn ( North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. ...
and
soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu ...
s have led to a massive reduction in weeds and native plants such as milkweeds. Subsequently, this has played a significant part in the population decline of the monarch butterfly. In 2018 the CEO of the
National Wildlife Federation The National Wildlife Federation (NWF) is the United States' largest private, nonprofit conservation education and advocacy organization, with over six million members and supporters, and 51 state and territorial affiliated organizations (includin ...
stated that the population of the monarch butterfly is now down 90 percent in the last 20 years and cited the reduction in milkweed as a contributing factor. Many parts of the United States face a reduction in milkweed population due to factors such as increased habitat loss due to development, roadside median mowing, and herbicide use. Despite this,
deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then land conversion, converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban area, urban ...
due to
human settlement In geography, statistics and archaeology, a settlement, locality or populated place is a community in which people live. The complexity of a settlement can range from a minuscule number of dwellings grouped together to the largest of cities ...
may have expanded the range and density of common milkweed in some regions. Milkweed has even become invasive as it is
naturalized Naturalization (or naturalisation) is the legal act or process by which a non-citizen of a country may acquire citizenship or nationality of that country. It may be done automatically by a statute, i.e., without any effort on the part of the i ...
in several areas outside of its original native range, including Oregon and some parts of Europe. Over 40 distinct
pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a ger ...
s of ''Asclepias'' species have been identified, including two dozen pathogens for ''A. syriaca''. For example, milkweed yellows is an
infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable d ...
caused by the milkweed yellows phytoplasma, a strain of
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
distinguished by the absence of a
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...
. The species features since 2017 on the list of Invasive Alien Species of Union Concern. This means that import of the species and trade in the species is forbidden in the whole of the
European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...
.


Cultivation

''A. syriaca'' can become invasive. It spreads aggressively from rhizomes and may not be suited to small gardens and formalized plantings. The plant is winter hardy in
USDA zone A hardiness zone is a geographic area defined as having a certain average annual minimum temperature, a factor relevant to the survival of many plants. In some systems other statistics are included in the calculations. The original and most wide ...
s 3–9; it has a preference for moist but well drained soils, but is tolerant of dry conditions and clay soils. It is ideal in semi-dry places where it can spread without presenting problems for other ornamental species. Monarch Watch provides information on rearing monarchs and their host plants. Efforts to restore falling monarch butterfly populations by establishing butterfly gardens and monarch migratory "waystations" require particular attention to the target species' food preferences and population cycles, as well to the conditions needed to propagate and maintain their food plants. In the northeastern United States, monarch reproduction peaks in late summer when most of the plant's leaves are old and tough. Plants that are mowed or cut back in June – August regrow rapidly from their rhizomes in time for peak monarch egg-laying, when reproducing female monarchs have a preference for quickly-growing ''A. syriaca'' shoots whose foliage is tender and soft. ''A. syriaca'' is easily propagated by both seed and rhizome cuttings. The plant's seeds require a period of cold treatment (
cold stratification In horticulture, stratification is a process of treating seeds to simulate natural conditions that the seeds must experience before germination can occur. Many seed species have an embryonic dormancy phase, and generally will not sprout until this ...
) before they will germinate. To protect seeds from washing away during heavy rains and from seed–eating birds, one can cover the seeds with a light fabric or with an layer of
straw Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has a numbe ...
mulch A mulch is a layer of material applied to the surface of soil. Reasons for applying mulch include conservation of soil moisture, improving fertility and health of the soil, reducing weed growth and enhancing the visual appeal of the area. A ...
. However, mulch acts as an insulator. Thicker layers of mulch can prevent seeds from germinating if they prevent soil temperatures from rising enough when winter ends. Further, few
seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (emb ...
s can push through a thick layer of mulch. Both seedlings and cuttings will usually bloom in their second year, although cuttings will occasionally bloom during their first year. The nonnative ''
Aphis nerii ''Aphis nerii'' is an aphid of the family Aphididae. Its common names include oleander aphid, milkweed aphid, sweet pepper aphid, and nerium aphid. Distribution The oleander aphid is widespread in regions with tropical and Mediterranean climate ...
'' (oleander aphid) can become abundant on milkweed shoots.


Uses

The plant's latex contains large quantities of
cardiac glycoside Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by inhibiting the cellular sodium-potassium ATPase pump. Their beneficial medical uses are as treatments for co ...
s, making the leaves and stems of old tall plants toxic to humans and large animals. The young shoots, young leaves, flower buds and immature fruits are all edible raw.
Euell Gibbons Euell Theophilus Gibbons (September 8, 1911 – December 29, 1975) was an outdoorsman and early health food advocate, promoting eating wild foods during the 1960s. Early career Gibbons was born in Clarksville, Texas, on September 8, 1911, a ...
, the author of ''Stalking the Wild Asparagus'' (1962), wrote that milkweed is bitter and toxic. However, he may have inadvertently prepared common dogbane (''
Apocynum cannabinum ''Apocynum cannabinum'' (dogbane, amy root, hemp dogbane, prairie dogbane, Indian hemp, rheumatism root, or wild cotton) is a perennial herbaceous plant that grows throughout much of North America—in the southern half of Canada and througho ...
''), a poisonous somewhat similar-looking plant instead. Gibbons devised a method to remove the bitterness and toxicity by plunging the young shoots into boiling water and cooking for one minute, repeating the procedure at least three times to make the plant safe to eat. Some modern foragers consider the bitterness and toxicity issue a myth. The plants have no bitterness when tasted raw, and can be cooked like asparagus, with no special processing. Failed attempts have been made to exploit rubber (from the latex) and fiber (from seeds' "floss") production from the plant industrially. The fluffy seed hairs have been used as the traditional background for mounted butterflies and other insects. The compressed floss has a silk-like sheen. The plant has also been explored for commercial use of its bast (inner bark) fiber, which is both strong and soft. U. S. Department of Agriculture studies in the 1890s and 1940s found that common milkweed has more potential for commercial processing than any other indigenous bast fiber plant, with estimated yields as high as hemp and quality as good as
flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known i ...
. Both the bast fiber and the floss were used historically by Native Americans for cordage and textiles. Milkweed has also been cultivated commercially to be used as insulation in winter coats. Traditionally, in both North America and Europe, the plant was used to treat respiratory infections such as
pleurisy Pleurisy, also known as pleuritis, is inflammation of the membranes that surround the lungs and line the chest cavity ( pleurae). This can result in a sharp chest pain while breathing. Occasionally the pain may be a constant dull ache. Other s ...
.


Genomics

The genome of ''A. syriaca'' has been sequenced. Genomic analysis of several hundred ''A. syriaca'' isolates from throughout the natural range in eastern North America showed that this species is a single panmictic population that experienced expansions about 12,000 years ago, after the recession of North American glaciers, and more recently, about 200 years ago, during clearing of forests for agriculture in the eastern United States.


Gallery

File:Asclepias syriaca 2019-04-21 1738.jpg, Seedling Common Milkweed Asclepias syriaca Unopened Flower Head 2223px.jpg, Buds in an umbelate cyme Common Milkweed (1035856056).jpg, Flowers File:Milk3.jpg, Leaves and young follicle Asclepias syriaca 004.JPG, Mature follicle Asclepias syriaca close up of the seed copy.jpg, Seeds emerging from a follicle Milkweedseeds.jpg, Seeds


Notes


References

* * * * *


External links

{{Taxonbar, from=Q158295
syriaca This list of Latin and Greek words commonly used in systematic names is intended to help those unfamiliar with classical languages to understand and remember the scientific names of organisms. The binomial nomenclature used for animals and plants i ...
Butterfly food plants Flora of North America Plants described in 1753 Taxa named by Carl Linnaeus Apocynaceae