''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 humans ...
'', 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 wid ...
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 (angiosperms ...
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
*Ovates, one of three ranks of membership in the Welsh Gorsedd
*Vates
In modern English, the nouns vates () and ova ...
-
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 regular ...
. 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 t ...
margins and reddish main veins. They have very short
petioles and velvety undersides.
The highly fragrant,
nectariferous flowers vary from white (rarely) through pinkish and purplish and occur in
umbellate
In botany, an umbel is an inflorescence that consists of a number of short flower stalks (called pedicels) that spread from a common point, somewhat like umbrella ribs. The word was coined in botanical usage in the 1590s, from Latin ''umbella'' " ...
cymes. 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 mil ...
. 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 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 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. I ...
''); other species that feed on the plant include red milkweed beetle (''
Tetraopes tetraophthalmus''), the milkweed tussock caterpillar (''
Euchaetes egle'') 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):65 ...
'' 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, 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 gener ...
'' 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.
...
e consume only milkweeds, and monarch populations may decline when milkweeds are eliminated with
herbicides.
The development and widely adopted cultivation of herbicide-resistant staple crops such as
corn 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 a ...
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 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 converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
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 ci ...
may have expanded the range and density of common milkweed in some regions.
Milkweed has even become
invasive as it is
naturalized 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 germ ...
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 di ...
caused by the
milkweed yellows phytoplasma
Milkweed yellows phytoplasma is a strain of phytoplasma in the class Mollicutes, a class of bacteria distinguished by the absence of a cell wall. The phytoplasma strain is denoted by the acronym MW1.
Like all phytoplasmas, milkweed yellows phy ...
, a strain of
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
distinguished by the absence of a
cell wall.
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 de ...
.
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 garden
Butterfly gardening is a way to create, improve, and maintain habitat for lepidopterans including butterflies, skippers, and moths. Butterflies have four distinct life stages—egg, larva, chrysalis, and adult. In order to support and sustain ...
s 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 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 mu ...
. 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 (embryo ...
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'' (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 c ...
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 ...
, 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 throughou ...
''), 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. 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 sy ...
.
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
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External links
{{Taxonbar, from=Q158295
syriaca
Butterfly food plants
Flora of North America
Plants described in 1753
Taxa named by Carl Linnaeus
Apocynaceae