Asclepias syriaca (common milkweed)
Publication: CABI Compendium
7249
Datasheet Types: Crop, Invasive species, Host plant, Pest
Abstract
This datasheet on Asclepias syriaca covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.
Identity
- Preferred Scientific Name
- Asclepias syriaca Blanco, 1837
- Preferred Common Name
- common milkweed
- Other Scientific Names
- Asclepias cornuti Decne.
- Asclepias intermedia Vail
- Asclepias kansana Vail
- Asclepias syriaca L. var. kansana (Vail) Palmer & Steyermark
- International Common Names
- Englishbroadleaf milkweedbutterfly flowercotton weedsilkweedsilky milkweedsilky swallow-wortVirginia silkweed milkweedwild cotton
- Spanishasclepiavencetosigo comun
- Frenchasclepiadeasclepiade de Syriecotonnierpetit-cochon
- Local Common Names
- GermanyGehoernte Seidenpflanze
- Netherlandszijdeplant
- EPPO code
- ASCSY (Asclepias syriaca)
Pictures
Habit
Asclepias syriaca (common milkweed); Habit. Petersham, Massachusetts, United States. August 2011.
©Alvin Kho/via Flickr - CC BY-SA 2.0
Flowering habit
Asclepias syriaca (common milkweed); Flowering habit. Rock Creek Park, Washington DC, USA. June 2019.
©Katja Schulz/via Flickr - CC BY-SA 2.0
Flower buds
Asclepias syriaca (common milkweed); Flower buds. Guelph, Ontario, Canada. July 2020.
©Ryan Hodnett/via Wikimedia Commons - CC BY-SA 4.0
Flower buds
Asclepias syriaca (common milkweed); Flower buds. Occoquan Regional Park, Lorton, Virginia, USA. June 2020.
©Judy Gallagher/via Flickr - CC BY-SA 2.0
Inflorescence
Asclepias syriaca (common milkweed); Inflorescence. French Creek Fen State Natural Area, Columbia County, Wisconsin, USA. June 2010.
©Joshua Mayer/via Flickr - CC BY-SA 2.0
Flowers and foliage
Asclepias syriaca (common milkweed); Flowers and foliage. Wrocław University Botanical Garden, Wrocław, Poland. June 2018.
©Agnieszka Kwiecień/via Wikimedia Commons - CC BY-SA 4.0
Inflorescence
Asclepias syriaca (common milkweed); Inflorescence. Mount Lebanon, Pennsylvania, USA. June 2015.
Public Domain- Released by Cbaile19/via Wikimedia Commons - CC0
Fruits
Asclepias syriaca (common milkweed); Fruits. Wrocław University Botanical Garden, Wrocław, Poland. August 2017.
©Agnieszka Kwiecień/via Wikimedia Commons - CC BY-SA 4.0
Fruits
Asclepias syriaca (common milkweed); Infructescence. Schleinbach, Austria. August 2015.
©Stefan Lefnaer (Stefan.lefnaer)/via Wikimedia Commons - CC BY-SA 4.0
Fruit
Asclepias syriaca (common milkweed); Fruit. Woodsdale, Ohio, USA. August 2014.
©Andrew Cannizzaro/via Flickr - CC BY 2.0
Seedhead
Asclepias syriaca (common milkweed); Seedhead. December 2004.
©Greg Hume/via Wikimedia Commons - CC BY-SA 4.0
Seeds
Asclepias syriaca (common milkweed); Seeds. October 2010.
©Brocken Inaglory/via Wikimedia Commons - CC BY-SA 3.0
Habit
Asclepias syriaca (common milkweed); Habit. Karnabrunn, Austria June 2012.
©Stefan Lefnaer (Stefan.lefnaer)/via Wikimedia Commons - CC BY-SA 4.0
Summary of Invasiveness
A. syriaca can be an aggressive and persistent weed and contains several poisonous glucosidic substances (cardenolides) known to be poisonous to sheep, cattle, and occasionally horses (Anderson, 1999).
Taxonomic Tree
Notes on Taxonomy and Nomenclature
Louis Hebert sent seeds of Asclepias syriaca from Quebec City, Canada to Paris and Cornut’s treatise published in 1635: ‘Canadensium plantarum aliarumque nondum editarum Historia’, describes both A. syriaca L. and A. incarnata L. A. syriaca was first identified as Apocynum majus syriacum rectum; Linnaeus then classified it as A. syriaca L. in 1753 (Gaertner, 1979).
Asclepias is a widespread genus with 76 species and 91 accepted taxa overall. There are 14 species of milkweed native in Canada (White, 1996). A. syriaca is the most widespread and locally abundant species of the genus (Hartzler and Buhler, 2000); it occurs in 38 states of North America.
According to Endress and Bruyns (2000) Asclepiadaceae is now treated as sub-family Asclepiadoideae in the family Apocynaceae.
Plant Type
Herbaceous
Perennial
Seed propagated
Vegetatively propagated
Description
A. syriaca (common milkweed) is a perennial herb with long-spreading rhizomes. Stems stout, erect, to 2 m tall, with short downy hairs and milky juice; leaves opposite, smooth margined, oblong, 10-20 cm long and 5-11 cm wide, with prominent veins; upper surface smooth, lower covered with short white hairs. Flowers sweet-smelling, pink to white, in large, many-flowered (the number per inflorescence varies greatly, from less than 10 to more than 120) axillary and apical bell-like clusters. The long-lived flowers produce copious amounts of nectar (Wyatt and Broyles, 1994), flowering from June to August, depending on initial growth, climate, and location (Anderson, 1999). Seed brown, flat, oval, 6 mm long, 5 mm wide, with a tuft of silky white hairs apically. All plant parts contain latex; shoots from established plants arise from adventitious root buds, emerging in April and May. The root system is composed of horizontal and vertical roots. In established stands, vertical roots may penetrate the soil to depths of 3.8 m (Anderson, 1999).
Distribution
Contrary to its specific name, A. syriaca is native to northeastern, north central and southeastern United States and adjacent areas of Canada, and has spread to cultivated areas (Hartzler Buhler, 2000). This plant grows throughout the Great Plains ecoregion from southern Canada south to northeastern Oklahoma, northwestern Georgia, and Texas; and east from North Carolina to Maine (USDA-NRCS, 2010). It is naturalized in cultivated ground and dry grassland in various parts of central and southern Europe (IENICA, 2003).
Distribution Map
Distribution Table
Means of Movement and Dispersal
Natural Dispersal (Non-Biotic)
Only 3% of A. syriaca flowers produce seed pods, as most fall from the inflorescence approximately 10 days after opening (Anderson, 1999). A. syriaca spreads mainly by seeds which are wind-dispersed on tufts of floss (Bhowmik, 1982). A. syriaca can produce large numbers of seeds, especially compared to other milkweed species, which facilitates dispersal over a long distance (White, 1996).
Pathway Causes
| Pathway cause | Notes | Long distance | Local | References |
|---|---|---|---|---|
| Research (pathway cause) | Yes | Gaertner (1979, publ. 1980) |
Pathway Vectors
| Pathway vector | Notes | Long distance | Local | References |
|---|---|---|---|---|
| Wind (pathway vector) | Yes | Yes |
Hosts/Species Affected
The crops most affected by this species are soybeans, corn, peanuts and grain sorghum (Anderson, 1999) and maize (Konstantinovic et al., 2008). Canadian studies of competition between common milkweed and oats found up to 20% yield loss of grain (Bhowmik, 1982).
Host Plants and Other Plants Affected
| Host | Family | Host status | References |
|---|---|---|---|
| Avena sativa (oats) | Poaceae | Main | |
| Glycine max (soyabean) | Fabaceae | Main | |
| Medicago sativa (lucerne) | Fabaceae | Main | |
| Solanum lycopersicum (tomato) | Solanaceae | Unknown | |
| Sorghum bicolor (sorghum) | Poaceae | Main | |
| Triticum aestivum (wheat) | Poaceae | Main | |
| Zea mays (maize) | Poaceae | Main |
Similarities to Other Species/Conditions
A. speciosa (showy milkweed) is similar to A. syriaca but it has broad, oval and rounded or heart-shaped leaves, densely woolly stalks, and fewer and longer flowers. Apocynum cannabinum (hemp dogbane) could be confused with A. syriaca but can be distinguished by its narrow, elliptical leaves 5-12 cm long, which are not hairy (Anderson, 1999). A. tuberosa (butterfly-weed) can also be mistaken for A. syriaca; it looks similar but it has orange flowers and the sap is not as milky.
Habitat
A. syriaca colonizes a variety of communities from woodlands to cleared grasslands and marshlands. It grows in clumps or patches in meadows, fencerows, roadsides, railways, waste places, reduced-tillage fields, and other open habitats.
Habitat List
| Category | Sub category | Habitat | Presence | Status |
|---|---|---|---|---|
| Terrestrial | ||||
| Terrestrial | Terrestrial – Managed | Cultivated / agricultural land | Principal habitat | Harmful (pest or invasive) |
| Terrestrial | Terrestrial – Managed | Managed grasslands (grazing systems) | Present, no further details | Harmful (pest or invasive) |
| Terrestrial | Terrestrial – Managed | Disturbed areas | Principal habitat | Harmful (pest or invasive) |
| Terrestrial | Terrestrial – Managed | Rail / roadsides | Principal habitat | Harmful (pest or invasive) |
| Terrestrial | Terrestrial ‑ Natural / Semi-natural | Natural grasslands | Present, no further details | Harmful (pest or invasive) |
Biology and Ecology
Genetics
A. syriaca is genetically self-incompatible, although low-levels of self-compatibility have been reported (Wyatt and Broyles, 1994), and this species has an unusual late-acting form of ovarian rejection. Flowers are self-sterile and insect-pollinated (Anderson, 1999), and pollen dispersal via a pollinium results with a fruit sharing the same outcrossed paternal parent (Hochwender, 2000). Only around 2% of the flowers produce mature pods, with an average plant producing 4-6 pods, containing approx. 150-425 seeds.
A. syriaca is genetically self-incompatible, although low-levels of self-compatibility have been reported (Wyatt and Broyles, 1994), and this species has an unusual late-acting form of ovarian rejection. Flowers are self-sterile and insect-pollinated (Anderson, 1999), and pollen dispersal via a pollinium results with a fruit sharing the same outcrossed paternal parent (Hochwender, 2000). Only around 2% of the flowers produce mature pods, with an average plant producing 4-6 pods, containing approx. 150-425 seeds.
Reproductive Biology
A. syriaca has a pollen delivery system whereby packets of pollen (pollinia) are transferred as a single unit during pollination; this method of reproduction is only seen elsewhere in some members of the Orchidaceae (Pleasants, 1991).The vegetative habit and weedy reproductive strategy A. syriaca makes it one of the most distinct milkweeds (Wilbur, 1976).
A. syriaca has a pollen delivery system whereby packets of pollen (pollinia) are transferred as a single unit during pollination; this method of reproduction is only seen elsewhere in some members of the Orchidaceae (Pleasants, 1991).The vegetative habit and weedy reproductive strategy A. syriaca makes it one of the most distinct milkweeds (Wilbur, 1976).
A. syriaca is pollinated by a wide range of insects, including bees, moths and butterflies (Howard, 2018). Pleasants (1991) found that much pollen dispersal in this species was short-distance.
In a study using isozyme polymorphisms to study multiple paternity in A. syriaca, Gold and Shore (1995) found no statistical evidence for multiple paternity within fruits but extensive multiple paternity between fruits on the same ramet, suggesting potential choice of mates through selective fruit abortion.
In a study using isozyme polymorphisms to study multiple paternity in A. syriaca, Gold and Shore (1995) found no statistical evidence for multiple paternity within fruits but extensive multiple paternity between fruits on the same ramet, suggesting potential choice of mates through selective fruit abortion.
Physiology and Phenology
A. syriaca grows as a colony of plants and each colony develops from a single plant arising from a seed or root segment, it has underground rootstocks that develop adventitious buds which give rise to new individuals; a large clonal group can comprise several thousand stems (Wilbur, 1976).
Vertebrate herbivores browse A. syriaca and results from a study by Hochwender (2000), showed that in low nutrient conditions, this species allocates resources to the storage organ, providing greater biomass when damaged; therefore an ability to compensate for damage might be important for this species.
A. syriaca grows as a colony of plants and each colony develops from a single plant arising from a seed or root segment, it has underground rootstocks that develop adventitious buds which give rise to new individuals; a large clonal group can comprise several thousand stems (Wilbur, 1976).
Vertebrate herbivores browse A. syriaca and results from a study by Hochwender (2000), showed that in low nutrient conditions, this species allocates resources to the storage organ, providing greater biomass when damaged; therefore an ability to compensate for damage might be important for this species.
Environmental Requirements
A. syriaca is adapted to wide range of climatic and edaphic conditions and will tolerate soil conditions in any textural group, but is most commonly found on well-drained soils of loamy texture and grows best in full sunlight or light shade. It does not tolerate excessive moisture. A. syriaca has been found to be the most abundant invasive species in open sand grasslands (Botta-Dukat, 2008).
A. syriaca is adapted to wide range of climatic and edaphic conditions and will tolerate soil conditions in any textural group, but is most commonly found on well-drained soils of loamy texture and grows best in full sunlight or light shade. It does not tolerate excessive moisture. A. syriaca has been found to be the most abundant invasive species in open sand grasslands (Botta-Dukat, 2008).
Climate
| Climate type | Description | Preferred or tolerated | Remarks |
|---|---|---|---|
| C - Temperate/Mesothermal climate | Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C | Preferred |
Air Temperature
| Parameter | Lower limit (°C) | Upper limit (°C) |
|---|---|---|
| Mean maximum temperature of hottest month | 18 | 32 |
Soil Tolerances
Soil texture > light
Soil texture > medium
Soil texture > heavy
Soil reaction > acid
Soil reaction > neutral
Soil reaction > alkaline
Soil drainage > free
List of Pests
Notes on Natural Enemies
Approximately 12 species of herbivore consume A. syriaca in eastern North America and nearly all are specialists of Asclepias spp. because of particular mandibular structures, feeding modes, and the way they avoid the defensive latex production of this species (Van Zandt and Agrawal, 2004).
Natural enemies
| Natural enemy | Type | Life stages | Specificity | References | Biological control in | Biological control on |
|---|---|---|---|---|---|---|
| Aphis nerii (sweet pepper aphid) | Herbivore | to genus | ||||
| Danaus plexippus (monarch butterfly) | Herbivore | to genus | ||||
| Labidomera clivicollis (milkweed leaf beetle) | Herbivore | to genus | ||||
| Liriomyza asclepiadis | Herbivore | to genus | ||||
| Lygaeus kalmii | Herbivore | to genus | ||||
| Rhyssomatus lineaticollis | Herbivore | to genus | ||||
| Tetraopes tetrophthalmus (red milkweed beetle) | Herbivore | to genus |
Impact Summary
| Category | Impact |
|---|---|
| Environment (generally) | Positive and negative |
Impact: Economic
Losses due to this species have been recorded in Sorghum production as A. syriaca populations increased (NAPPO, 2003). The floss attached to seeds also tends to clog air intake devices on combines during harvest (Anderson, 1999).
Impact: Environmental
Impact on Biodiversity
A. syriaca can be an aggressive and persistent weed and contains several poisonous glucosidic substances (cardenolides) known to be poisonous to sheep, cattle, and occasionally horses (Anderson, 1999). All parts of the plant contain the potentially toxic substances and A. syriaca is toxic to poultry; some milkweeds have been declared ‘noxious weeds’ in some North America states (White, 1996).
The specialist herbivores Tetraopes tetraophthalmus and Danaus plexippus have developed adaptations that allow them to sequester plant-generated cardenolides to defend themselves against predators (Hochwender et al., 2000).
Populations of the plant are thought to be beneficial as a source of nectar for butterflies, bees and other insects and A. syriaca plays an important part in the life cycle of the monarch butterfly (Danaus plexippus). Since D. plexippus requires A. syriaca as a larval food (Urquhart and Urquhart, 1979), D. plexippus might be at risk in Canada if noxious weed legislation were to be enforced and resulted in the elimination of milkweed (Hartzler and Buhler, 2000).
Risk and Impact Factors
Invasiveness
Invasive in its native range
Proved invasive outside its native range
Has a broad native range
Abundant in its native range
Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
Pioneering in disturbed areas
Has high reproductive potential
Reproduces asexually
Impact outcomes
Negatively impacts agriculture
Negatively impacts animal health
Impact mechanisms
Allelopathic
Causes allergic responses
Uses
Economic Value
A. syriaca is considered medicinal in the USA and foliage or latex is used as a remedy for cancer, tumours and warts. It is also thought to be beneficial in treating asthma, catarrh and cough. Good quality fibre is obtained from the inner bark of the stem and can be used to make twine.
Uses List
Environmental > Wildlife habitat
Materials > Fibre
Materials > Rubber/latex
Medicinal, pharmaceutical > Traditional/folklore
Human food and beverage > Oil/fat
Human food and beverage > Vegetable
Prevention and Control
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Control
Physical/mechanical control
Removal of stalks by cutting can aggravate the problem as this stimulates growth from underground buds, and when cultivated, the resulting small root fragments will grow into a new plant.
Chemical control
Seedlings can be controlled with selected herbicides as pre-emergence treatments Bhowmik (1982). Aboveground plant parts may be destroyed by herbicides including 2, 4-D, mecoprop, dicamba and MCPA, but growth of adventitious roots is stimulated by this action. Amitrole-T and glyphosate will kill top growth and result in restricted regrowth during the following season. Glyphosate seems to be most effective overall and may reduce A. syriaca occurrence in crop fields (NAPPO, 2003).
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References
Anderson WP, 1999. Perennial weeds. Characteristics and identification of selected herbaceous species. Iowa, USA: Iowa State University Press, 228 pp.
Bhowmik PC, 1982. Herbicide control of common milkweed (Asclepias syriaca). Weed Science, 30:349-351.
Botta-Dukát Z, 2008. Invasion of alien species to Hungarian (semi-)natural habitats. Acta Botanica Hungarica, 50(Supplementum):219-227. http://www.akademiai.com
DAISIE, 2010. European Invasive Alien Species Gateway. European Invasive Alien Species Gateway. http://www.europe-aliens.org
Endress ME, Bruyns PV, 2000. A revised classification of the Apocynaceae s.l. Botanical Review, 66(1):1-56.
GBIF, 2010. Global Biodiversity Information Facility. Global Biodiversity Information Facility. GBIF. http://data.gbif.org/species/
Gaertner EE, 1979, publ. 1980. The history and use of milkweed (Asclepias syriaca L.). Economic Botany, 33(2):119-123.
Gold JJ, Shore JS, 1995. Multiple paternity in Asclepias syriaca using a paired-fruit analysis. Canadian Journal of Botany, 73(8):1212-1216.
Hartzler RG, Buhler DD, 2000. Occurrence of common milkweed (Asclepias syriaca) in cropland and adjacent areas. Crop Protection, 19(5):363-366.
Hochwender CG, Marquis RJ, Stowe KA, 2000. The potential for and constraints on the evolution of compensatory ability in Asclepias syriaca. Oecologia, 122(3):361-370.
Howard, A. F., 2018. Asclepias syriaca (common milkweed) flowering date shift in response to climate change.Scientific Reports, 8(1) 17802.
IENICA, 2003. Milkweed, Interactive European Network for Industrial Crops and their Applications (IENICA). Milkweed, Interactive European Network for Industrial Crops and their Applications (IENICA). http://www.ienica.net/crops/milkweed.pdf
Jeffery LS, Robison LR, 1971. Growth characteristics of common milkweed. Weed Science, 19(3):193-6.
Konstantinovic B, Meseldzija M, Mandic N, 2008. Distribution of Asclepias syriaca L. on the territory of Vojvodina and possibilities of its control. Herbologia, 9(2):39-46. http://www.anubih.ba/index.php?option=content&lang=eng&Theme=herbologia&Level=2&ItemID=7
NAPPO, 2003. Pest fact sheet Asclepias syriaca L. North American Plant Protection Organization (NAPPO). http://www.nappo.org/PRA-sheets/Asclepiassyriaca.pdf
Pleasants JM, 1991. Evidence for short-distance dispersal of pollinia in Asclepias syriaca L. Functional Ecology, 5(1):75-82.
Timmons FL, 1946. Studies of the distribution and floss yield of Common Milkweed (Asclepias syriaca L.) in Northern Michigan. Ecology, 27(3):212-225.
USDA-NRCS, 2010. The PLANTS Database. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/
White DJ, 1996. Status, distribution, and potential impact from noxious weed legislation. Report prepared for the Canadian Wildlife Service, Ottawa, Canada. Status, distribution, and potential impact from noxious weed legislation. Report prepared for the Canadian Wildlife Service, Ottawa, Canada. http://www.monarchwatch.com/read/articles/canweed1.htm
Wilbur HM, 1976. Life history evolution in seven milkweeds of the genus Asclepias. Journal of Ecology, 64(1):223-240.
Wyatt R, Broyles SB, 1994. Ecology and evolution of reproduction in milkweeds. Annual Review of Ecological Systematics, 25:423-441.
Zandt PAvan, Agrawal AA, 2004. Community-wide impacts of herbivore-induced plant responses in milkweed (Asclepias syriaca). Ecology, 85(9):2616-2629. http://www.esajournals.org/perlserv/?request=get-document&doi=10.1890%2F03-0622
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Published online: 1 March 2010
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